Water-repellent film and method for preparing the same, and ink-jet head and ink-jet type recording device using the same

ABSTRACT

A water-repellent film that is formed on a solid substrate includes: a molecule (A) including at least one or more of siloxane bonding (—Si—O—) at both ends and a hydrocarbon chain in a middle part; and a molecule (B) including a fluorocarbon chain at one end and at least one or more of siloxane bonding (—Si—O—) at another end, wherein a polymer film is formed at least with the molecule (A) and the molecule (B). This polymer film forms a covalent bond with a surface of the substrate via siloxane bonding (—Si—O—), and the surface thereof is covered with fluorocarbon chains having high water repellency. Therefore, this film prevents the intrusion of alkali ions. Thereby, an ink jet head and an ink jet type apparatus having a water-repellent film that is not destroyed by the long-term contact with alkaline ink can be provided.

TECHNICAL FIELD

[0001] The present invention relates to a water-repellent film havinghigh alkali resistance and a method for producing the same. The presentinvention also relates to an ink jet head and an ink jet type recordingapparatus using the water-repellent film.

BACKGROUND ART

[0002] A water-repellent film, which can repel water and oil and alloweasy removal of materials attached to the surface thereof, has been usedwidely in various fields. For example, by forming a water-repellent filmon windows of an automobile, it is possible to secure an excellent viewbecause the windows can repel water even on rainy days.

[0003] Furthermore, by forming a water-repellent film on such places asthe surface of cooking equipment, kitchen, bathroom, and the like, dirtcan be removed easily from such places, and consequently, the carethereof becomes easy. Furthermore, in recent years, such awater-repellent film has been used as a main component of an ink jetnozzle making up an ink jet head of an ink jet type recording apparatus.The reason why the ink jet nozzle requires a water-repellent film willbe described below in detail.

[0004] The mechanism of printing by the ink jet type recording apparatusis to discharge several tens pico-liter of ink from each of a largenumber of nozzle holes with a diameter of several tens μm, which arebored in a nozzle plate, onto a printed medium such as paper so as toarrange the discharged ink at a predetermined position on the printedmedium. In order to arrange the ink at a predetermined position on theprinted medium, the ink is discharged while mechanically moving thenozzle plate and the printed medium respectively to control theirrelative position. FIG. 8A is a cross-sectional view showing a nozzlehole 34 and its vicinity, where an ink space 31 for storing a fixedamount of ink 32 is formed on an inner surface of a nozzle plate 33having a through hole from which the ink 32 is discharged. As shown inFIG. 8B, the ink space 31 is designed so that the pressure in the spacecan be increased as needed, for example, by means of mechanicaldeformation of a piezoelectric thin film 35. By increasing the pressurein the ink space 31, a predetermined amount of ink 36 can be dischargedthrough the through hole of the nozzle plate from the ink space asindicated by an arrow 37. Here, in order to conduct high-definitionprinting, the ink discharged from the through hole should be arranged onthe printed medium accurately. To this end, it is necessary to controlprecisely the relative position of the nozzle and the printed medium, tocontrol the amount of discharged ink and make the same minute, and tocontrol precisely the discharging direction of the ink. Among these, inorder to control precisely the discharging direction of the ink, thedischarging direction of the ink should be perpendicular to the nozzleplate face. Here, as shown in FIG. 9A, if ink 45 remains at a portion ofthe periphery of the hole, the discharging direction of ink 47 will leantoward the remaining ink side and deviate from the perpendiculardirection as shown by an arrow 48 of FIG. 9B. Because the attractiveforce occurs due to the surface tension between the ink 47 and theremaining ink 45, the ink 47 from the nozzle 34 is attracted toward theside of the ink 45. To avoid this situation, in normal printers,remaining ink is removed by wiping the periphery of holes regularly witha rubber blade. Here, in order to clearly remove the remaining ink bywiping it with the rubber blade, it has been found that anink-discharging plane of a nozzle plate should have water repellency.For that reason, on a surface of an ink jet nozzle plate, variouswater-repellent films are formed.

[0005] Conventionally, in order to form a water-repellent film on asolid substrate, in general, polytetrafluoroethylene (PTFE) and thederivatives thereof, which have water repellency, have been applied tothe substrate to form a film. However, PTFE and the derivatives thereofhave a small surface energy and even if they are applied directly to thesubstrate to form a film, the film peels off the substrate easily.Therefore, in order to secure the adhesion between the film and thesubstrate, there have been employed a method of roughening the surfaceof the substrate and then applying a water-repellent film to theroughened surface, and a method of roughening the surface of thesubstrate, and forming a primer layer (adhesive layer) made ofpolyethylene sulphide, etc., on the roughened surface, followed bysintering a water-repellent film. Furthermore, when the solid substrateis made of a metal, a method of plating particles of PTFE and thederivatives thereof together with the metal may be employed.

[0006] On the other hand, there have been proposed methods of forming awater-repellent film having an excellent adhesion directly on thesurface of a substrate by using a silane coupling agent withoutroughening the surface of the substrate. As the first example of thesemethods, there is described a method for forming a water-repellentmonomolecular or polymer film by allowing fluoroalkyl trichlorosilanesuch as CF₃(CF₂)₈C₂H₄SiCl₃ to react with a substrate (JP 2500816 and JP2525536). In the above-mentioned chemical formula, CF₃(CF₂)₈C₂H₄—represents a fluoroalkyl group, and —SiCl₃ represents a trichlorosilylgroup. In this method, a substrate having active hydrogen on the surfacethereof is brought into contact with a solution in which fluoroalkyltrichlorosilane is dissolved so as to allow a chlorosilyl group (—SiCl)to react with active hydrogen, thus forming —Si—O— bonding to thesubstrate. As a result, a fluoroalkyl chain is fixed to the substratevia —Si—O—. Herein, the fluoroalkyl chain provides a film with waterrepellency. Depending on the film formation conditions, thewater-repellent film becomes a monomolecular film or a polymeric film.As the second example, there is described a method in which a poroussubstrate impregnated with a compound containing fluorine such asfluoroalkyl alkoxysilane is heated in a vacuum to evaporate thecompound, thus providing the surface of the substrate with waterrepellency (JP 6 (1994)-143586A). In order to improve the adhesionbetween the water-repellent film and the substrate, this method proposesthat an intermediate layer made of silicon dioxide, etc. is provided. Asthe third example, there is described a method of forming a film made oftitanium, titanium oxide or indium-tin oxide on the substrate, andforming a fluoroalkyl silane based compound thereon by a vacuumevaporation method (JP 10 (1998)-323979A). As the fourth example, thereis described a method of forming fine particles of oxides such aszirconia and alumina on the surface of a substrate, and then applying afluorine based silane coupling agent such as fluoroalkyl chlorosilaneand fluoroalkyl alkoxysilane (JP 6 (1994)-171094A). As the fifthexample, there is described a method of subjecting a mixed solution,which is obtained by adding metal alkoxide to fluoroalkylalkoxysilanesuch as CF₃(CF₂)₈C₂H₄Si(OCH₃)₃, to hydrolysis and dehydrationpolymerization, and then applying the solution to the substrate,followed by baking, thereby forming a water-repellent film in whichmolecules having a fluoroalkyl chain are mixed in the metal oxide (JP2687060, JP 2874391, JP 2729714 and JP 2555797). In these methods, afluoroalkyl chain provides the film with water repellency, and a metaloxide provides the film with a high mechanical strength.

[0007] The water repellent film has to be produced by selecting anoptimum method among various formation methods as described abovedepending on its intended use. For the formation of a water-repellentfilm used for an ink jet nozzle, especially, a method utilizing a silanecoupling agent is more effective than the other methods because of thefollowing respects. Firstly, a water-repellent treatment can beconducted basically on any substrate of a nozzle. Secondly, awater-repellent film can be made thin. The reason for requiring the thinfilm is, as shown in FIG. 10A, that side faces of a nozzle through hole34 that is bored in a water-repellent film 55 should have waterrepellency and have a small film thickness. A large film thickness of awater-repellent film 56 as shown in FIG. 10B makes it impossible for ink32 to be discharged from an ink space 31 through a through hole 34 dueto the water repellency of the side faces thereof. To avoid thissituation, the film thickness should be made sufficiently smaller than anozzle diameter. For this reason, it can be considered that the secondfeature will increasingly become important. This is because the tendencyfor requiring high-definition printing will be increased in the future,and accordingly a nozzle diameter will be reduced, and therefore awater-repellent film with a film thickness smaller than such a nozzlediameter will be demanded. Therefore, the above-mentioned second tofourth methods are employed for forming a water-repellent film used foran ink jet nozzle.

[0008] Since a water-repellent film using a silane coupling agent can beformed on various substrates without performing a pretreatment, it canbe expected to be applied in various fields. It is particularly usefulin an ink jet head application. However, a conventional water-repellentfilm using a silane coupling agent lacks durability against alkalinity.Especially, in the application to an ink jet head, this is a seriousproblem. This is because the ink used for an ink jet type recordingapparatus generally is alkaline, and therefore a water repellent-filmused for the ink jet head is required to have durability against analkaline solution.

[0009] The conventional monomolecular film or polymer film using asilane coupling agent is bonded to the substrate via Si—O bonding.However, since this bonding is hydrolyzed easily in an alkalinesolution, when the conventional water-repellent film is soaked in analkaline solution, the bonding disappears easily from the substrate.That is, such a film lacks durability against an alkaline solution.

[0010] Then, the third and fourth examples provide a method in which inorder to improve the alkali resistance, an alkali resistant lower filmmade of titanium oxide, titanium, zirconia particles, alumina particles,etc. is formed under a water-repellent film. Thus, a water-repellentfilm hardly is peeled off the solid substrate due to the lower layerbreaking away. On the other hand, even with this configuration, theproblem that hydrogen bonding or siloxane bonding between thewater-repellent film and the substrate is broken by alkaline has notbeen solved completely.

[0011] The water-repellent films proposed in the conventional methodsuse a silane coupling agent having a reactive group only at one end of astraight-chain molecule, for example, fluoroalkyl alkoxysilane andfluoroalkyl chlorosilane, etc. In such a coupling agent, as shown inFIG. 11, due to the steric hindrance between molecules,three-dimensional polymerization between molecules hardly occurs and thefilm density is lower than that of a general polymeric polymer. A silanecoupling agent 61 causes a hydration reaction 62 with a hydroxyl groupon the surface of the substrate to form siloxane bonding, or is fixed byhydrogen bonding. Therefore, as shown in FIG. 12A, as the substrate 71has the higher density of hydroxyl groups on the surface of thesubstrate, the density of the film (a film of the silane coupling agentbonded to the substrate) 72 in the vicinity of the substrate becomeshigher. Herein, as shown in FIG. 12B, in the case of a lower film 73made of titanium oxide, titanium, zirconia, etc., since the density ofhydroxyl groups on the surface of such a film is low, the density of thewater-repellent film (a film of the silane coupling agent bonded to thesubstrate) 74 that is in contact with the lower film is low. FIG. 13 isa schematic view showing a state in which water-repellent films 82 and81 formed on a lower layer 83 having a low density of hydroxyl groupsare exposed to an alkaline component. In the nearer part of the lowerfilm 83, the silane coupling molecules (a water-repellent film in thevicinity of the lower film) 82 are fixed to the lower film 83 viahydrogen bonding and siloxane bonding, and in the more distant part fromthe lower film 83, the low density water-repellent film (awater-repellent film distant from the lower film) 81 is formed. When analkali ink is brought into contact with this film, hydroxyl ions (OH—)84 as alkaline components pass through the film 81 and go to the lowerfilm 83. When the density of the water-repellent film 82 in the vicinityof the lower film is small, ions 85 enter into the interface between thefilm 82 and the lower film 83 and break the hydrogen bonding and thesiloxane bonding present therein. Even if the lower film has muchdurability against an alkaline solution, if the density of hydroxylgroups on the surface thereof is low, the alkali resistance of thewater-repellent film decreases.

[0012] Furthermore, in order to improve the alkali resistance, the fifthexample is useful, in which a molecule having a fluoroalkyl chain ismixed in the metal oxide such as titanium oxide and zirconium oxide,which has the durability against an alkaline solution. However, thesemetal oxides have to be produced by subjecting titanalkoxide andzirconiumalkoxide to hydrolysis and dehydration polymerization, andthese alkoxides have high reactivity and hydrolysis proceeds quickly inthe air. Therefore, it is hard to handle a coating solution using thesealkoxides for applying a water-repellent film. Therefore,siliconalkoxide that is stable in the air has been used widely. However,silicon oxide formed from the siliconalkoxide is solved in an alkalinesolution. Therefore, there is a problem that the water-repellent filmusing siliconalkoxide has low durability against an alkaline solution.

DISCLOSURE OF THE INVENTION

[0013] In order to cope with the above-stated problems, an object of thepresent invention is to provide a water-repellent film having alkaliresistance and a method for producing the same. Furthermore, anotherobject of the present invention is to provide, by applying thiswater-repellent film, an ink jet head and an ink jet type apparatusincluding an ink jet nozzle provided with a water-repellent film that isnot broken after the long time contact with an alkaline ink.

[0014] To fulfill the above-stated object, a first water-repellent filmof the present invention that is formed on a solid substrate includes: amolecule (A) including at least one or more of siloxane bonding (—Si—O—)at both ends and a hydrocarbon chain in a middle part; and a molecule(B) including a fluorocarbon chain at one end and at least one or moreof siloxane bonding (—Si—O—) at another end, wherein a polymer film isformed at least with the molecule (A) and the molecule (B).

[0015] A second water-repellent film of the present invention is formedon a solid substrate and is made up of a two-layered thin film. In thewater-repellent film, a first-layer film contacting with the substrateis made of a mixture of a silicon oxide and a titanium oxide, a ratio ofthe silicon to the titanium being in the range from 10% to 30%,inclusive, in terms of mols, and a second-layer film formed on thefirst-layer film is a polymer film that is at least one selected from ahydrolyzate and a dehydrated polymer of a silane coupling agentcomprising a fluorocarbon chain.

[0016] Next, a first method for producing a water-repellent film on asolid substrate of the present invention includes the steps of: applyinga coating solution to the substrate, wherein the coating solution isprepared by mixing a silane coupling agent (A) including reactivefunctional groups at both ends and comprising a hydrocarbon chain in amiddle part, a silane coupling agent (B) including a fluorocarbon chainat one end and a reactive functional group at another end, an organicsolvent, water and an acidic catalyst, and heating the substrate so asto form a polymer film with the silane coupling agent (A) and the silanecoupling agent (B).

[0017] A second method for producing a water-repellent film on a solidsubstrate includes the steps of: applying a first coating solution tothe substrate, followed by baking at 300° C. or higher, where the firstcoating solution is prepared by mixing titanalkoxide, siliconalkoxide,an organic solvent, water and an acidic catalyst, and applying a secondcoating solution to the substrate, followed by baking, where the secondcoating solution is prepared by mixing a silane coupling agent having afluorocarbon chain, an organic solvent, water and an acidic catalyst. Inthe first coating solution, a ratio of the siliconalkoxide to thetitanalkoxide is in the range from 10% to 30%, inclusive, in terms ofmols.

[0018] Next, an ink jet nozzle of the present invention includes asubstrate having a nozzle hole from which ink is discharged and awater-repellent film that is formed on an ink-discharging side of thesubstrate. Here, the water-repellent film is the water-repellent filmaccording to any one of the first to second water-repellent films of thepresent invention.

[0019] Next, an ink jet type recording apparatus of the presentinvention includes the ink jet head according to any one of theabove-described ink jet heads and a moving unit for relative movement ofa recording medium.

BRIEF DESCRIPTION OF DRAWINGS

[0020]FIG. 1 is a schematic view showing a configuration of awater-repellent film according to Embodiment 1 of the present invention.

[0021]FIG. 2 schematically shows a state where a water-repellent filmaccording to Embodiment 4 of the present invention, which is formed on asolid substrate, is exposed to an alkaline component.

[0022]FIG. 3 is a schematic view showing a process in which a highdensity polymer film is formed according to Embodiment 5 of the presentinvention.

[0023]FIG. 4 is a schematic view showing a state of the surface of asubstrate that is exposed to a solution containing straight-chainmolecules according to Embodiment 5 of the present invention.

[0024]FIG. 5A is a schematic view showing a state right after a coatingsolution containing a silane coupling agent having a fluoroalkyl chainis exposed to a substrate, FIG. 5B is a schematic view showing a statewhere the silane coupling agent having a fluoroalkyl chain is absorbedto the surface of the substrate and C is a schematic view showing astate of the surface of the substrate repelling the coating solution.

[0025]FIG. 6 is a cross-sectional view of a nozzle and the vicinityaccording to Embodiment 9 of the present invention.

[0026]FIG. 7 is a perspective view of an ink jet type recordingapparatus according to Embodiment 11 of the present invention.

[0027]FIG. 8A is a cross-sectional view of a nozzle hole and thevicinity according to the conventional example, and FIG. 8B is across-sectional view schematically showing a state in which an ink spacetherein increases in pressure so as to discharge ink from the hole.

[0028]FIG. 9A is a cross-sectional view schematically showing a state inwhich ink remains at a nozzle hole according to the conventionalexample, and FIG. 9B is a cross-sectional view schematically showing acase where ink is discharged when ink remains at the nozzle hole.

[0029]FIG. 10A is a cross-sectional view showing a nozzle plate and thevicinity when a film thickness of the water-repellent film is smallaccording to the conventional example, and FIG. 10B is a cross-sectionalview showing a nozzle plate and the vicinity when a film thickness ofthe water-repellent film is large.

[0030]FIG. 11 is a schematic view showing a polymerization of a silanecoupling agent having a reaction group at only one end according to theconventional example.

[0031]FIG. 12A is a schematic view showing a configuration of a silanecoupling agent bonded to a substrate having hydroxyl groups at highdensity on the surface thereof according to the conventional example,and FIG. 12B is a schematic view showing a configuration of a silanecoupling agent bonded to a substrate having hydroxyl groups at lowdensity on the surface thereof according to the conventional example.

[0032]FIG. 13 is a schematic view showing a state in which awater-repellent film formed on a lower layer having a low density ofhydroxyl groups according to the conventional example is exposed to analkaline component.

BEST MODE FOR CARRYING OUT THE INVENTION

[0033] In the water-repellent film of the present invention, between thesolid substrate and the water-repellent film, a first lower polymer filmfurther may be formed, the first lower polymer film being configuredwith a molecule including at least one or more of siloxane bonding(—Si—O—) at both ends and a fluorocarbon chain in a middle part.

[0034] In addition, between the solid substrate and the first lowerpolymer film, a second lower oxide film may be formed, the second loweroxide film being made of a mixture of a silicon oxide and a titaniumoxide.

[0035] In addition, it is preferable that a density of the molecule (B)in the vicinity of the outermost surface of the water-repellent film ishigher than a density of the molecule (B) inside the water-repellentfilm.

[0036] In addition, in the water-repellent film of the presentinvention, it is preferable that a ratio of the molecule (A) and themolecule (B) is in the range from 0.001 to 0.2 (=the molecule (B)/themolecule (A)) that is represented by a mol ratio.

[0037] In addition, in the water-repellent film of the presentinvention, the molecule (A) may include a straight-chain hydrocarbonchain. Alternatively, in the water-repellent film of the presentinvention, the molecule (A) may include a benzene ring.

[0038] Next, in the method of the present invention, between the solidsubstrate and the water-repellent film, a polymer film further may beformed by applying a first underlayer coating solution to the substrate,wherein the first underlayer coating solution is prepared by mixing asilane coupling agent including reactive functional groups at both endsand including a fluorocarbon chain in a middle part, an organic solvent,water and an acidic catalyst.

[0039] It is preferable that after the first underlayer coating solutionis applied to the solid substrate, followed by heating at 100° C. to300° C., inclusive, then a coating solution including the silanecoupling agent (A) and the silane coupling agent (B) is applied thereto.

[0040] Between the solid substrate and the first underlayer polymerfilm, an oxide film that is made of a silicon oxide and a titanium oxidefurther may be formed by applying a second underlayer coating solutionto the substrate, followed by baking, wherein the second underlayercoating is prepared by mixing titanalkoxide, siliconalkoxide, an organicsolvent, water and an acidic catalyst.

[0041] In addition, in the method of the present invention, when themolecule (A) includes a hydrocarbon chain, it is preferable that thenumber of carbons that constitute the straight-chain hydrocarbon chainranges from 1 to 10, inclusive. In the present invention, it ispreferable that the molecule (A) includes a benzene ring and a mol ratioof water/the molecule (A)=20 to 150 is satisfied. In the method of thepresent invention, it is preferable that a mol ratio of the molecule (A)and the molecule (B) is in the range from 0.001 to 0.2 (=the molecule(B)/the molecule (A)).

[0042] In the method of the present invention, it is preferable that theorganic solvent of the coating solution including the silane couplingagent (B) includes alcohol having fluorocarbon.

[0043] In addition, in the method of the present invention, it ispreferable that a dew point of the atmosphere for applying the coatingsolution to the substrate is lower than a temperature of the atmosphereby 5° C. or more.

[0044] In addition, in the method of the present invention, it ispreferable that when the molecule (A) includes a straight-chainhydrocarbon chain, it is preferable that the number of carbons thatconstitute the straight-chain hydrocarbon chain ranges from 1 to 10,inclusive.

[0045] In addition, in the method of the present invention, it ispreferable that a method for applying the coating solution to a surfaceof the substrate is at least one selected from a dipping method, aspraying method, a brushing method, a method using a cloth, a spincoating method, a method using a roller, a knife coating method and afilm coating method.

[0046] As a result of various analyses and experiments by the presentinventors as to an influence of an alkaline solution on awater-repellent film and its mechanism, the present inventors have founda method for realizing a water-repellent film having high alkaliresistance using a silane coupling agent. In addition, an ink jet headand an ink jet type recording apparatus can be realized by applying thiswater-repellent film.

[0047] The following describes embodiments of the present invention forthe sake of clarity of the present invention. However, the presentinvention is not limited only to the following embodiments.

[0048] [Embodiment 1]

[0049] According to the first embodiment of the present invention, afilm includes a molecule (A) having at least one or more of siloxanebonding (—Si—O—) at both ends and a hydrocarbon chain (—(CH₂)_(n)—; n isa natural number) in the middle part and a molecule (B) having afluorocarbon chain (—(CF₂)_(n); n is a natural number) at one end and atleast one or more of siloxane bonding (—Si—O—) at another end, where apolymer is formed with the molecule (A) and the molecule (B). Thefluorocarbon chain of the molecule (B) provides the film with waterrepellency, because it is a nonpolar molecule. Then, the molecule (A)forms a high-density polymer film by the siloxane bonding at the bothends of the molecule, and the molecule (B) is bonded to this polymerfilm via the siloxane bonding.

[0050] As one example of the molecule (A), —OSi(R¹R²)(CH₂)_(n)Si(R¹R²)O—(R¹ and R² are a methyl group, an ethyl group, a methoxy group (—OCH₃),an ethoxy group (—OC₂H₅), a hydroxyl group (—OH), or oxygen constitutingsiloxane bonding, and n is a natural number from 1 to 10) is included.As the molecule (B), CF₃(CF₂)_(n)C₂H₄Si(R¹R²)O— (R¹ and R² are a methylgroup, an ethyl group, a methoxy group (—OCH₃), an ethoxy group(—OC₂H₅), a hydroxyl group (—OH), or oxygen constituting siloxanebonding, and n is a natural number from 1 to 12) is included. Herein, inorder to provide the film with high water repellency, in the molecule(B), n=6 to 10 is preferable.

[0051]FIG. 1 is a schematic view showing a configuration of awater-repellent film 1 as one example of the present invention. In thisexample, the molecule (A) is (—O—)₃Si(CH₂)₆Si(—O—)₃ and the molecule (B)is CF₃(CF₂)₇C₂H₄Si(—O—)₃. In this configuration, the density of themolecule (B) is high in the vicinity of a surface of the water-repellentfilm. Therefore, even when a ratio of the molecule (B) to the molecule(A) is low, a film with high water repellency can be obtained. As theratio of the molecule (B) decreases, the film density of thewater-repellent film is improved. Therefore, the water-repellent film ofthe present invention has excellent wear resistance. In FIG. 1, as asubstrate 2, metal, ceramics and the like can be used.

[0052] In this film, siloxane bonding (—Si—O—) is present. Generally,the siloxane bonding is hydrolyzed in an alkaline solution and isdisconnected. However, the present inventors have found that in theconfiguration of the water-repellent film of the present invention, thewater-repellent hydrocarbon chain and fluorocarbon chain are present inthe vicinity of the siloxane bonding and these molecule chains preventan alkaline solution from intruding into the film. The present inventorshave found that, as a result of this, the water-repellent film is notbroken even in the presence of alkaline agents.

[0053] As the number of carbons constituting straight-chain hydrocarbonchain of the molecule (A) increases, the chain increasingly prevents thealkaline component from intruding into the siloxane bonding, butconversely, the density of the film decreases, thus decreasing the wearresistance of the film. The present inventors have found that, when thenumber of carbons constituting the straight-chain hydrocarbon chain ofthe molecule (A) ranges from 1 to 10, a film with excellent alkaliresistance and excellent wear resistance can be realized.

[0054] As the ratio of the molecule (B) increases, the water repellencyof the film is improved, but the wear resistance thereof decreases.Conversely, as the ratio of the molecule (B) decreases, the wearresistance of the film is improved but the water repellency thereofdecreases. The present inventors have found that when the mol ratio ofthe molecule (B)/the molecule (A)=0.001 to 0.2 is satisfied, a film withexcellent water repellency and excellent wear resistance can berealized.

[0055] When the molecule (A) includes a benzene ring, heat resistance ofthe water-repellent film is improved because the benzene ring has highheat resistance. That is, when the middle part of the molecule (A)includes only the straight-chain hydrocarbon chain, the water-repellentcoating film exhibits heat-resistance of about 250° C., whereas thewater-repellent coating film including a benzene ring exhibitsheat-resistance of 300° C. or higher. Furthermore, the moleculeincluding a benzene ring is stiffer than a molecule that does notinclude a benzene ring (the flexibility permissible for the molecularstructure is reduced), and therefore this molecule is packed densely andthe film density is increased, thus improving the wear resistance.

[0056] As the molecule (A) having a benzene ring,—OSi(R¹R²)(CH₂)_(t)C₆H₄(CH₂)_(u)Si(R³R⁴)O— (R¹, R², R³ and R⁴ are amethyl group, an ethyl group, a methoxy group (—OCH₃), an ethoxy group(—OC2H₅), a hydroxyl group (—OH), or oxygen constituting siloxanebonding, and t and u are a natural number from 1 to 10) is included.Herein, in order to improve the heat resistance of the produced film, itis preferable that the length of the straight-chain hydrocarbon chain ismade as small as possible and t and u range from 1 to 3.

[0057] [Embodiment 2]

[0058] The second embodiment of the present invention is configured witha two-layered thin film. That is, a first-layer film is a polymer thatis made up of a molecule having at least one or more of siloxane bonding(—Si—O—) at both ends and a fluorocarbon chain in the middle part, and asecond-layer film formed on the first-layer film includes a molecule (A)having at least one or more of siloxane bonding (—Si—O—) at both endsand a hydrocarbon chain in the middle part and a molecule (B) having afluorocarbon chain at one end and at least one or more of siloxanebonding (—Si—O—) at another end, where a polymer is formed with themolecule (A) and the molecule (B). Herein, the configuration of thesecond-layer film is basically the same as that of the film used inEmbodiment 1.

[0059] As the molecule having a fluorocarbon chain in the middle part,—OSi(R¹R²)C₂H₄(CF₂)_(n) C₂H₄Si(R³R⁴)O— (R¹, R², R³ and R⁴ are a methylgroup, an ethyl group, a methoxy group (—OCH₃), an ethoxy group(—OC₂H₅), a hydroxyl group (—OH), or oxygen constituting siloxanebonding, and n is a natural number from 1 to 12) is included. In thefirst-layer polymer made up of this molecule, siloxane bonding isincluded. However, the water-repellent fluorocarbon chain in thevicinity of this bonding prevents an alkaline solution from intrudinginto the film, thus preventing the breakage of the siloxane bonding bythe alkaline solution. As a result, this polymer film can havedurability against an alkaline solution. Furthermore, the moleculehaving a fluoroalkyl chain in the middle part is stiffer than a moleculehaving a hydrocarbon chain in the middle part (the flexibilitypermissible for the molecular structure is reduced), and therefore thismolecule is packed densely and the film density is increased, thusimproving the wear resistance and strengthening a bonding force with asubstrate.

[0060] The present inventors have found that this first-layer filmserves as an adhesive layer between the substrate and the second-layerfilm. Especially, in the case of a substrate made of platinum and micahaving a small density of hydroxyl groups on the surface thereof, whenthe second-layer film is formed directly thereon, the adhesion of thefilm is low. On the contrary, the provision of the adhesive layer canimprove the adhesion of the water-repellent film.

[0061] [Embodiment 3]

[0062] The third embodiment of the present invention is configured witha three-layered thin film. That is, a first-layer film that contactswith a substrate is made of a mixture of a silicon oxide and a titaniumoxide. A second-layer film formed on the first layer film is a polymerthat is made up of a molecule having at least one or more of siloxanebonding (—Si—O—) at both ends and a fluorocarbon chain in the middlepart, and a third-layer film formed on the second-layer film includes amolecule (A) having at least one or more of siloxane bonding (—Si—O—) atboth ends and a hydrocarbon chain in the middle part and a molecule (B)having a fluorocarbon chain at one end and at least one or more ofsiloxane bonding (—Si—O—) at another end, where a polymer is formed withthe molecule (A) and the molecule (B).

[0063] Herein, the film configuration of the second-layer film and thethird-layer film is basically the same as that shown in Embodiment 2.

[0064] The silicon oxide and the titanium oxide have higher hardness ascompared with the second-layer and third-layer polymer films, and havebetter adhesion with the substrate. The present inventors have foundthat the titanium oxide film provides the film with alkali resistanceand the silicon oxide film functions so as to improve the adhesionbetween the substrate and the second-layer film. Then, the presentinventors have found that the first-layer film is made of the mixture oftitanium and silicon, and the second-layer and third-layer films areformed thereon, whereby an alkali resistant water-repellent film havinghigh adhesion with the substrate can be formed.

[0065] Furthermore, in the water-repellent film of this embodiment, thefirst-layer film completely prevents an alkaline solution from intrudinginto the substrate, and therefore by forming the water-repellent film ona substrate having low alkali resistance, the alkali resistance of thesubstrate can be improved.

[0066] [Embodiment 4]

[0067] The fourth embodiment of the present invention is configured witha two-layered thin film. That is, a first-layer film that contacts witha substrate is made of a mixture of a silicon oxide and a titaniumoxide, where a ratio of the silicon to the titanium is in the range from10% to 30% in terms of mols, and a second-layer film formed on thefirst-layer film is made up of a hydrolyzate and/or a dehydrated polymerof a silane coupling agent having a fluorocarbon chain.

[0068] When the silicon oxide film alone is included, the adhesiondensity to the second-layer film is high because high-density silanolgroups (—SiOH) are present on the surface thereof, but the film lacksalkali resistance. When the titanium oxide film alone is included, theadhesion density of the film is lower because the density of hydroxylgroups on the surface is lower compared to the silicon oxide film, butthe alkali resistance is improved. The present inventors have foundthat, when the ratio of silicon atoms to titanium atoms in thefirst-layer film is within a range of 10% to 30% in terms of mols, theadhesion density to the second-layer film is high and the alkaliresistance is improved.

[0069]FIG. 2 shows one example of a water-repellent film according tothis embodiment. In FIG. 2, reference numeral 21 denotes the first-layerfilm, 22 denotes the second-layer film, 23 denotes a portion of thewater-repellent film in the second-layer film that is distant from thefirst-layer film and 24 denotes a portion of the water-repellent film inthe second-layer film that is near to the first-layer film. In this filmstructure, the water-repellent film 24 made of the second-layer film,located near to the first-layer film has a high density, so that thefilm does not peel off the first layer due to alkaline components 26that intrude through the water-repellent film 23 as the portion of thesecond-layer film that is distant from the first-layer film. Here, inFIG. 2, reference numeral 25 denotes an ion of the alkaline componentthat intrudes into the water-repellent film.

[0070] [Embodiment 5]

[0071] The fifth embodiment of the present invention relates to a methodfor producing a water-repellent film on a solid substrate, in which asilane coupling agent (A) having reactive functional groups at both endsand including a hydrocarbon chain in the middle part; a silane couplingagent (B) having a fluorocarbon chain at one end and a reactivefunctional group at another end; an organic solvent; water and an acidiccatalyst are mixed to produce a coating solution, and this coatingsolution is applied to the substrate, followed by heating of thesubstrate, so as to form a polymer with the silane coupling agent (A)and the silane coupling agent (B).

[0072] In the organic solvent, water and acidic catalyst, a couplingpart, —Si—X (X represents an alkoxyl group, chlorine, acyloxy, or amine)of the silane coupling agent participates in the reactions expressed bythe following chemical formulae Formula 1 to Formula 3.

—Si—X+H₂O→—Si—OH+HX  (Formula 1)

—Si—X+—Si—OH→—Si—O—Si—+HX  (Formula 2)

—SiOH+—SiOH→—Si—O—Si—+H₂O  (Formula 3)

[0073] The reaction expressed by Formula 1 shows the generation of asilanol group (Si—OH) by hydrolysis; Formulas 2 and 3 show thegeneration of a siloxane bonding (—Si—O—) by a dehydrationpolymerization, respectively.

[0074] Right after a predetermined amount of silane coupling agent,organic solvent, water and acid catalyst are mixed, the reactionsexpressed by the chemical formulas Formula 1 to Formula 3 occur.Therefore, the coating solution contains a hydrolyzate, a dehydratedpolymer, or a molecule having unreacted reactive functional groups ofthe silane coupling agent, which are mixed therein. Since the reactionsof the Formula 1 to Formula 3 proceed quickly, the coating solution canbe applied to the substrate right after the preparation of the coatingsolution. However, the temperature of the coating solution increasesright after mixing due to the heat resulting from chemical reaction,which might cause variations in the application state, and therefore itis desirable that the application is conducted after 1 to 2 hours havepassed after mixing. When this coating solution is applied to thesubstrate, a film is formed on the substrate. Right after theapplication, the film includes the silane coupling agent, solvent,water, and acid catalyst. However, when the substrate is heated at 100°C. or more, the solvent, water and acid catalyst are evaporated, andaccordingly, unreacted reactive functional groups become silanol or thedehydration polymerization reaction between silanol groups proceeds. Asa result, a solid thin film is formed on the substrate.

[0075] As shown in FIG. 3, since the silane coupling agent (A) 11 hasreactive functional groups at both ends of the molecule, dehydrationpolymerization reaction takes place in a portion as shown by an arrow 12so as to form a high density three-dimensional polymer film. Therefore,the formed film has a structure in which the silane coupling agent (B)is fixed to the three-dimensional polymer film of the silane couplingagent (A) via siloxane bonding. Note here that in the film, the silanecoupling agent (A) and the silane coupling agent (B) are bonded to eachother via siloxane bonding to form a polymer film. However, in the film,unreacted reactive functional groups or silanol groups (Si—OH) mayremain. The higher the baking temperature is, the fewer of these groupsremain. Furthermore, when hydroxyl groups (—OH) are present on thesurface of the substrate, the silane coupling agent causes a dehydrationreaction with the hydroxyl groups to form siloxane bonding or hydrogenbonding. Therefore, the water-repellent film is fixed to the substratefirmly.

[0076] Note here that, in the present invention, right after theapplication of the coating solution, the silane coupling agent (A) formsthe three-dimensional polymer film, whereas the silane coupling agent(B) moves across the film due to the thermal diffusion. This movement isfinished at the time when a liquid component in the film is evaporatedaway to some extent. As a result of this movement, the density of thesilane coupling agent (B) increases on the surface of the film. That isto say, in an aggregation of materials having various surface energylevels, it is known that the materials having different surface energyvalues cause phase separation therebetween, and materials having closerlevels tend to gather. Since the hydrocarbon chain included in thesilane coupling agent (A) and the fluorocarbon chain included in thesilane coupling agent (B) repel each other, phase separation is likelyoccur in the film. On the other hand, right after the application of thecoating solution to the substrate, the surface of the coating solutioncontacts with air, and the surface energy of the air is the smallestamong all materials. The fluorocarbon chain in the silane coupling agent(B) has the smallest surface energy in the coating solution. Therefore,although the silane coupling agent (B) in the coating solution moves invarious directions, when it reaches the surface of the coating solutionand the molecule contacts with air having smaller surface energy, thismolecule becomes fixed. As a result, the silane coupling agent (B)generates the phase separation from the silane coupling agent (A) whilebeing fixed near the surface of the film. This means that even when theamount of the silane coupling agent (B) in the coating solution isreduced relative to the silane coupling agent (A), the density of thefluorocarbon chain increases at the surface of the film, so that thefilm exhibits water repellency. In order to realize a film with highwear resistance, it is important that the film with high waterrepellency can be obtained even when the ratio of the silane couplingagent (B) is small. This is because the silane coupling agent (B) has areactive functional group only at one end of the molecule, which makesit difficult to form a three-dimensional polymer film. Therefore, whenthe ratio of the silane coupling agent (B) in the film increases, thedensity of the film decreases, thus decreasing the wear resistancethereof.

[0077] As the silane coupling agent (A),X_(s)Q_(3-s)Si(CH₂)_(n)SiR_(3-m)X_(m) in which alkoxyl groups arepresent at both ends of a straight-chain hydrocarbon is preferable (Qand R represent a methyl group or an ethyl group; n represents a naturalnumber between 1 and 10; s and m represent a natural number between 1and 3, when s=1 and m=1 are satisfied, two Qs and Rs are presentrespectively, but each of the two Qs and Rs may have a differentstructure).

[0078] Furthermore, when the silane coupling agent (A) includes abenzene ring, the heat resistance of the water-repellent film isimproved because the benzene ring has high heat resistance. Furthermore,the molecule including a benzene ring is stiffer as compared with amolecule that does not include a benzene ring (the flexibilitypermissible for the molecular structure is reduced), and therefore thismolecule is packed densely and the film density is increased, thusimproving the wear resistance. The silane coupling agent (A) including abenzene ring includes X_(s)Q_(3-s)Si(CH₂)_(t)C₆H₄(CH₂)_(u)SiR_(3-m)X_(m)(Q and R represent a methyl group or an ethyl group; t and u represent anatural number between 1 and 10; s and m represent a natural numberbetween 1 and 3, when s=1 and m=1 are satisfied, two Qs and Rs arepresent respectively, but each of the two Qs and Rs may have a differentstructure). Herein, in order to improve the heat resistance of theproduced film, it is preferable that the straight-chain hydrocarbonchain is made as short as possible and t and u range from 1 to 3.

[0079] Note here that, as the number of carbons constituting thestraight-chain hydrocarbon chain of the silane coupling agent (A)increases, the chain increasingly prevents the alkaline component fromintruding into the siloxane bonding, but conversely the density of thefilm decreases, thus decreasing the wear resistance. The presentinventors have found that, when the number of carbons constituting thestraight-chain hydrocarbon chain of the molecule (A) ranges from 1 to10, a film with excellent alkali resistance and excellent wearresistance can be realized.

[0080] Furthermore, the silane coupling agent (B) includesCF₃(CF₂)_(n)C₂H₄SiR_(3-m)X_(m) (R represents a methyl group or an ethylgroup; n represents a natural number between 1 and 12; m represents anatural number between 1 and 3, when m=1 is satisfied, two Rs arepresent, but each of the two Rs may have a different structure). Herein,in order to provide a film with high water repellency, n=6 to 10 ispreferable.

[0081] Note here that, as the ratio of the silane coupling agent (B)increases, the water repellency of the film is improved, but converselythe wear resistance thereof decreases. Conversely, as the ratio of themolecules (B) decreases, the wear resistance of the film is improved butthe water repellency thereof decreases. The present inventors have foundthat when the mol ratio of the silane coupling agent (B)/the silanecoupling agent (A)=0.001 to 0.2 is satisfied, a film with excellentwater repellency and excellent wear resistance can be realized.

[0082] In order to apply the coating solution to the substrate so as toform a film, the coating solution desirably has fluidity. To this end,it is desirable that only a part of the silane coupling agents in thecoating solution is polymerized. This is because if all of the silanecoupling agents are polymerized, the coating solution becomes a gel (asolid state including some liquid characteristics, exemplified by agar,bean curd, etc.) and loses fluidity, making it impossible to apply it tothe substrate. In the case where X of the silane coupling agent ischlorine, the reactivity of the coupling part is too high. Therefore,unless the amount of water is strictly controlled, the coating solutioneasily becomes a gel. On the contrary, in the case where X is an alkoxylgroup, hydrolysis and dehydration polymerization reaction proceed slowlyin the presence of water and acid, so that the coating solution can beapplied to the substrate easily.

[0083] In order to carry out hydrolysis and dehydration polymerizationreaction of a silane coupling agent having silane coupling parts of α innumber per molecule completely so as to form a three-dimensionalpolymer, water molecules of α/2 in number are required for one moleculeof the silane coupling agent, as determined theoretically from theformulas Formula 1 to Formula 3. Practically, however, even when thetheoretically required amount of water is present, the silane couplingparts do not react completely, and the degree of progress of thereaction will be different depending on the types of the silane couplingagents. This is because the reaction speed of Formula 1 to Formula 3 isvaried depending on the conditions such as the three-dimensionalstructure of molecules of the silane coupling agent, the types offunctional groups located in the vicinity of the silane coupling parts,and the types of the catalyst. Generally, however, as the amount ofwater molecules increases, the reaction speed increases. If the amountof water is increased too much, the polymerization of the silanecoupling agent proceeds excessively, resulting in the failure ofdissolving it in the coating solution, which causes the tendency of thecoating solution to become cloudy. When the cloudy coating solution isapplied to the substrate, a uniform film cannot be obtained. The presentinventors have found that, in the case of the silane coupling agent (A)having a benzene ring, if the mol ratio of water/molecule (A)=20 to 150is satisfied, the silane coupling agent can react sufficiently so thatthe coating solution does not get cloudy, whereby a film with excellentwear resistance, in which three-dimensional polymerization proceedssufficiently, can be formed.

[0084] In order to form a uniform film by applying the coating solutionto the substrate, it is necessary for the coating solution to have asufficient wettability with the substrate. Meanwhile, when a solution,in which straight-chain molecules having a flouoroalkyl chain at one endand a hydrophilic group at the other end are dissolved, is exposed to asubstrate, the straight-chain molecules are absorbed to the substrate sothat the hydrophilic group side is directed to the substrate side andthe fluoroalkyl chain side is directed to the opposite side. As aresult, the surface of the substrate exhibits water repellency. Since apart of the silane coupling agent (B) of the coating solution ishydrolyzed to have a hydrophilic silanol group, when the coatingsolution is applied to the substrate, the silane coupling agent isabsorbed to the outermost surface of the substrate (FIG. 4). In FIG. 4,reference numeral 91 denotes a solution in which straight-chainmolecules are dissolved, 92 denotes the straight-chain molecules in thesolution, 93 denotes a straight-chain molecule that is absorbed to thesurface of a substrate, 94 denotes the substrate, 95 denotes awater-repellent portion of the straight-chain molecule and 96 denotes ahydrophilic portion of the straight-chain molecule. Due to thisconfiguration, the surface of the substrate has water repellency, so asto repel the coating solution (FIGS. 5A to C), resulting in the failureof the uniform application of the coating solution to the substrate. Thepresent inventors have found that, even in the case of the coatingsolution including a silane coupling agent having a fluoroalkyl chain,the surface tension of the coating solution can be reduced by mixingalcohol including fluorocarbon therewith, whereby the wettability withthe substrate remarkably can be improved. In FIGS. 5A to C, referencenumeral 121 denotes a coating solution, 122 denotes a substrate, 123denotes a surface exhibiting water repellency and 124 indicates acoating solution in the state where the coating solution has reducedwettability with the substrate so as to be repelled against the surfaceof the substrate.

[0085] Furthermore, as a result of the detailed examination by thepresent inventors as to the procedure for applying the coating solutionto the substrate so as to form a thin film, it has been found that, whena dew point of the atmosphere for applying the coating solution to thesubstrate is lower than the temperature of the atmosphere by 5° C. ormore, a uniform film can be produced on the substrate. The reason forthis will be described below. That is to say, after the coating solutionis applied to the substrate, an organic solvent in the coating solutionis evaporated, and the heat caused by the evaporation lowers thetemperature of the substrate. Therefore, the surface temperature of thesubstrate becomes lower than the atmosphere to which the substrate isexposed. When the temperature difference between the surface of thesubstrate and the atmosphere is increased, the water vapor contained inthe atmosphere condenses on the surface of the substrate. This occursfrom the same principal as in the phenomenon in which, when cold drinkis poured into a glass on a hot day in the summer, water droplets areformed on an outer side of the glass. If the condensation of watercontents occurs on the substrate, the surface tension of the coatingsolution increases, which deteriorates the wettability of the coatingsolution to the substrate. As a result, it becomes difficult to form auniform film. As a result of the repetition of various experiments bythe present inventors, it has been found that when a dew point of theatmosphere is lower than the temperature of the atmosphere by 5° C. ormore, the condensation does not occur on the surface of the substrate.

[0086] [Embodiment 6]

[0087] The sixth embodiment of the present invention relates to a methodfor producing a water-repellent film on a solid substrate. The methodincludes the steps of: applying a first coating solution to thesubstrate, where the first coating solution is prepared by mixing asilane coupling agent having reactive functional groups at both ends andincluding a fluorocarbon chain in the middle part, an organic solvent,water and an acidic catalyst; applying a second coating solution to thesubstrate, where the second coating solution is prepared by mixing asilane coupling agent (A) having reactive functional groups at both endsand including a hydrocarbon chain in the middle part, a silane couplingagent (B) having a fluorocarbon chain at one end and a reactivefunctional group at another end, an organic solvent, water and an acidiccatalyst; and heating of the substrate so as to form a polymer with thesilane coupling agent (A) and the silane coupling agent (B).

[0088] As the silane coupling agent in the first coating solution, forexample, X_(s)Q_(3-s)SiC₂H₄(CF₂)_(n) C₂H₄SiR_(3-m)X_(m) (X represents analkoxyl group, Q and R represent a methyl group or an ethyl group; nrepresents a natural number between 1 and 10; s and m represent anatural number between 1 and 3, when s=1 and m=1 are satisfied, two Qsand Rs are present respectively, but each of the two Qs and Rs may havea different structure). Generally, a fluorine atom in the compound has ahigh electronegativity, having a property of attracting electrons of aneighbor atom. In the silane coupling agent of the present inventionalso, a fluorine atom attracts electrons from a neighbor atom, resultingin the shortage state in electrons of silicon. As a result, the bondingbetween the silicon and X becomes ionic bonding, in which hydrolysisproceeds easily. Therefore, the reactivity of the silane coupling agenthaving a fluorocarbon chain is higher than that of the silane couplingagent including a hydrocarbon chain only, and hydrolysis and dehydrationpolymerization reaction proceeds sufficiently, so that thepolymerization degree of the film increases and the film become robust.Furthermore, when the substrate includes hydroxyl groups, the siloxanebonding with the substrate is easy to be formed, so that the film can befixed to the substrate firmly. Moreover, the fluorocarbon chain is stiff(the flexibility permissible for the molecular structure is reduced),and therefore this silane coupling agent is packed densely, thus makingthe film robust.

[0089] The coating solution for the second layer is the same as thecoating solution described in Embodiment 5. Right after the applicationof the first coating solution to the substrate, there are a number ofsilanol groups in a hydrolyzed state in the silane coupling agent. Forthat reason, when the second coating solution is applied to this,followed by baking, then the silane coupling agent in the second coatingsolution forms the siloxane bonding with the silane coupling agent inthe first coating solution so that these two films are boned to eachother firmly. The present inventors have found that, as a result ofthese steps, the first-layer film functions as an adhesion layer betweenthe second-layer film and the substrate, so that the water-repellentfilm can be bonded to the substrate firmly.

[0090] Here, when the first coating solution and the second coatingsolution are applied continuously, the temperature of the final bakingcannot be made higher than the heat-resistant temperature of thesecond-layer film. This is because the heat resistance of thesecond-layer film having the hydrocarbon chain is lower than that of thefirst-layer film. Thus, after the first coating film is applied to thesolid substrate, followed by the heating at 100° C. to 300° C.,inclusive, the second coating solution is applied to the substrate,whereby the density of the first-layer film and the adhesion of the sameto the substrate can be improved. In this case also, since there are anumber of silanol groups on the surface of the first-layer film afterbaking, the adhesion between the first-layer film and the second-layerfilm is high.

[0091] This embodiment is especially effective for forming awater-repellent film with high adhesion on a substrate with a lowdensity of hydroxyl groups on the surface thereof, such as platinum andmica.

[0092] [Embodiment 7]

[0093] The seventh embodiment of the present invention relates to amethod for producing a water-repellent film on a solid substrate. Themethod includes the steps of: applying a first coating solution to thesubstrate, followed by baking, where the first coating solution isprepared by mixing titanalkoxide, siliconalkoxide, an organic solvent,water and acidic catalyst; applying a second coating solution to thesubstrate, where the second coating solution is prepared by mixing asilane coupling agent having reactive functional groups at both ends andincluding a fluorocarbon chain in the middle part, an organic solvent,water and an acidic catalyst; applying a third coating solution to thesubstrate, where the third coating solution is prepared by mixing asilane coupling agent (A) having reactive functional groups at both endsand including a hydrocarbon chain in the middle part, a silane couplingagent (B) having a fluorocarbon chain at one end and a reactivefunctional group at another end, an organic solvent, water and an acidiccatalyst; and heating of the substrate so as to form a polymer with thesilane coupling agent (A) and the silane coupling agent (B).

[0094] The titanalkoxide includes titanium tetraethoxide (Ti(OC₂H₅)₄),titanium tetra normal propoxide (Ti(OC₂H₄CH₃)₄), titanium tetraisopropoxide (Ti(OCHCH₃CH₃)₄), titanium tetra normal butoxide(Ti(OC₃H₆CH₃)₄), etc. The siliconalkoxide includes tetra methoxysilane(Si(OCH₃)₄), tetra ethoxysilane (Si(OC₂H₅)4), etc. Here, thetitanalkoxide generally has high reactivity, generating hydrolysis anddehydration polymerization reaction with a small amount of water, whichmakes the coating solution unstable. Therefore, in order to suppress thereaction of the titanalkoxide, an inhibitor is added to the coatingsolution. As the inhibitor, for example, a β-diketone compound such asacetylacetone and acetoace tic ester, and amine are available. When thefirst coating solution is applied to the substrate, followed by baking,then a mixed film of titanium oxide (TiO_(x); 0<X≦2) and silicon oxide(SiO_(y); 0<y>2) is formed. After that, the second and the third coatingsolutions are applied to this film in the same manner as in Embodiment6, whereby a water-repellent film having alkali resistance can beformed.

[0095] Here, the titanium oxide in the first-layer film provides thefilm with alkali resistance. The silicon oxide has a silanol group, andby virtue of the hydrogen bonding or the siloxane bonding of thissilanol group, the second-layer film can be bonded to the first-layerfilm firmly. As a result of examinations by the present inventors sofar, it has been found that, in the case where the first layer does notcontain silicon oxide at all, if the water-repellent film is soaked inan alkaline solution for a long time, then the second layer sometimespeels off the first layer. In addition, the present inventors have foundthat, in the case where a water-repellent film is formed on a substratemade of such as platinum and mica with reduced oxide film and activeoxygen on the surface thereof, this first-layer film is effective.

[0096] As the temperature for baking the first layer is increased, thefilm with better adhesion with the substrate and higher alkaliresistance can be formed. Preferable temperatures are 300° C. to 500° C.

[0097] This embodiment is especially effective for forming awater-repellent film on a glass or a ceramic with reduced alkaliresistance.

[0098] [Embodiment 8]

[0099] The eighth embodiment of the present invention relates to amethod for producing a water-repellent film on a solid substrate. Themethod includes the steps of: applying a first coating solution to thesubstrate, followed by baking at 300° C. or higher, where the firstcoating solution is prepared by mixing titanalkoxide, siliconalkoxide,an organic solvent, water and acidic catalyst; applying a second coatingsolution to the substrate, where the second coating solution is preparedby mixing a silane coupling agent having a fluorocarbon chain, anorganic solvent, water and an acidic catalyst; and heating the substrateat 100° C. or higher. In the first coating solution, a ratio of thesiliconalkoxide to the titanalkoxide ranges from 10% to 30% in terms ofmols.

[0100] Similarly to Embodiment 7, the titanalkoxide includes titaniumtetraethoxide (Ti(OC₂H₅)₄), titanium tetra normal propoxide(Ti(OC₂H₄CH₃)₄), titanium tetra isopropoxide (Ti(OCHCH₃CH₃)₄), titaniumtetra normal butoxide (Ti(OC₃H₆CH₃)₄), etc. The siliconalkoxide includestetra methoxysilane (Si(OCH₃)₄), tetra ethoxysilane (Si(OC₂H₅)₄), etc.Here, the titanalkoxide generally has high reactivity, generatinghydrolysis and dehydration polymerization reaction with a small amountof water, which makes the coating solution unstable. Therefore, in orderto suppress the reaction of the titanalkoxide, an inhibitor is added tothe coating solution. As the inhibitor, for example, a β-diketonecompound such as acetylacetone and acetoacetic ester, and amine areavailable. When the first coating solution is applied to the substrate,followed by baking, then a mixed film of titanium oxide (TiO_(x); 0<X≦2)and silicon oxide (SiO_(y); 0<y≦2) is formed. In addition, similarly toEmbodiment 5, the silane coupling agent having a fluorocarbon chainincludes CF₃(CF₂)_(n)C₂H₄SiR_(3-m)X_(m) (R represents a methyl group oran ethyl group; n represents a natural number between 1 and 12; mrepresents a natural number between 1 and 3, when m=1 is satisfied, twoRs are present, but each of the two Rs may have a different structure).Herein, in order to provide a film with high water repellency, n=6 to 10is preferable. In addition, in order to control the reaction of thecoating solution favorably, X is preferably an alkoxyl group. Moreover,in order to form a higher density film, m preferably equals 3.

[0101] In the silane coupling agent in which an alkoxysilyl group isbonded only to one end of a fluorine straight-chain molecule, it isdifficult to form a three-dimensional polymerized film, and the densityof the film is lower than that of the film of Embodiment 1 and thereforean alkaline solution easily penetrates through the film. The presentinventors, however, have found that, when a ratio of silicon atoms totitanium atoms in the titanium and silicon oxide film as the first layeris in the range from 20% to 30% in terms of mols, sufficient hydroxylgroups are present so that the silane coupling agent in the second layercan be attached thereto with high density, and moreover the film hasresistance against an alkaline solution.

[0102] As the temperature for baking the first layer is increased, thefilm with better adhesion with the substrate and higher alkaliresistance can be formed. Preferable temperatures are 300° C. to 500° C.

[0103] [Embodiment 9]

[0104] The ninth embodiment of the present invention relates to an inkjet nozzle. As shown in FIG. 6, this embodiment includes as constructioncomponents a nozzle plate 33 having a nozzle hole 34 from which ink isdischarged and an ink jet nozzle 30 in which a water-repellent film 39is formed on an ink-discharging side of the plate. As thewater-repellent film, the water-repellent film described in Embodiments1 to 4 is used.

[0105] [Embodiment 10]

[0106] The tenth embodiment of the present invention relates to a methodfor producing an ink jet nozzle, in which a water-repellent film isformed on a nozzle plate by the methods of Embodiments 5 to 8 of thepresent invention.

[0107] [Embodiment 11]

[0108] The eleventh embodiment of the present invention relates to anink jet type recording apparatus. FIG. 7 schematically shows the overallconfiguration of an ink jet type recording apparatus having an ink jethead of the present invention. An ink jet type recording apparatus 140of this drawing is equipped with an ink jet head 141 of the presentinvention that conducts recording utilizing a piezoelectric effect by apiezoelectric element. Drops of ink that are discharged from this inkjet head 141 arrive on a recording medium 142 such as paper, wherebyrecording is conducted on the recording medium 142. The ink jet head 141is mounted on a carriage 144 that is provided along a carriage axis 143arranged in the main scanning direction X. In accordance withreciprocating motion of the carriage 144 along the carriage axis 143,the ink jet head 141 also performs reciprocating motion in the mainscanning direction X. The ink jet type recording apparatus 140 furtherincludes a plurality of rollers (moving means) 145 that move therecording medium 142 relatively in the sub-scanning direction Y that issubstantially perpendicular to the width direction of the ink jet head141 (i.e., the main scanning direction X).

[0109] The following describes specific examples of the presentinvention. Note here that the present invention is not limited to thefollowing examples.

EXAMPLE 1

[0110] A stainless substrate (SUS304) having a size of 5 cm×5 cm and athickness of 0.2 mm was used as a substrate. A coating solution wasprepared by mixing chemical substances having the following components:

[0111] (1) Ethanol: 60 ml

[0112] (2) 1,6-bis(trimethoxysilyl)hexane ((CH₃O)₃Si(CH₂)₆Si(OCH₃)₃): 4ml

[0113] (3) (2-perfluorooctyl)ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 1 ml

[0114] (4) Water: 1 ml

[0115] (5) Hydrochloric acid (36 vol %): 0.1 ml

[0116] The mixed solution of these was applied to the substrate by spincoating. The spin coating was carried out at 800 rpm for 20 seconds.Thereafter, the substrate was dried at room temperatures for 1 hour,followed by baking at 200° C. for 30 minutes. Here, the environmentduring spin coating was set at a temperature at 24° C. and a relativehumidity of 34%. A dew point in this environment was 5° C.

[0117] Here, for reference, water-repellent coating films were producedusing conventionally used methods.

(a) COMPARATIVE EXAMPLE 1 (CONVENTIONAL EXAMPLE 1)

[0118] 400 ml of reactive solution was prepared in which lvol % of(2-perfluorooctyl)ethyltrichlorosilane (CF₃(CF₂)₇C₂H₄SiCl₃) wasdissolved in perfluorooctane and this solution was poured into a 500ml-beaker. In addition, three 500 ml-beakers were prepared, andapproximately 400 ml of perfluorooctane was poured into each of thebeakers.

[0119] Next, a substrate was soaked in the beaker containing thereactive solution for 2 hours. Thereafter, the substrate was taken outand was washed in the beaker containing perfluorooctane. The washing wasconducted using the three beakers sequentially. As a result, amonomolecular film of fluoroalkyl trichlorosilane was formed on thesubstrate. These operations were all performed in a glove box filledwith a dry nitrogen atmosphere.

(b) COMPARATIVE EXAMPLE 2 (CONVENTIONAL EXAMPLE 2)

[0120] A coating solution was prepared by mixing chemical substanceshaving the following components:

[0121] (1) Ethanol: 100 ml

[0122] (2) Tetraethoxysilane (Si(OC₂H₅)₄): 25 ml

[0123] (3) (2-perfluorooctyl)ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 4 ml

[0124] (4) Water: 7 ml

[0125] (5) Hydrochloric acid (36 vol %): 0.4 ml

[0126] This coating solution was applied to the substrate by spincoating under the condition at 3,000 rpm for 20 seconds. Thereafter, thesubstrate was baked at 300° C. for 30 minutes.

[0127] Evaluations of the water-repellent films were conducted in termsof the following three items:

[0128] Evaluations of Water Repellency

[0129] (1) A static contact angle of the water-repellent film to purewater was measured.

[0130] (2) Alkali resistance: A substrate to which a water repellentfilm has been applied was soaked in a buffer solution of pH=8.0 and wasallowed to stand at 80° C. for 100 hours. Then, the substrate was takenout and a static contact angle to pure water was measured. Note herethat the buffer solution was prepared by appropriately mixing thefollowing solutions A and B so that the mixed solution had pH=8.0.

[0131] Solution A: 0.2 M boric acid, 0.2 M potassium chloride

[0132] Solution B: 0.2 M sodium carbonate

[0133] (3) Evaluations of wear resistance

[0134] A cloth (cotton 100%) wetted with water was pressed against awater-repellent film under a load of 2×10⁵ dyn/cm² (about 0.2 kgweight/cm²), and the water-repellent film was rubbed with the cloth bymoving it back and forth for 1,000 times. A static contact angle of thethus rubbed water-repellent film to pure water was measured.

[0135] The results of the evaluations of the water-repellent filmprepared in this Example are shown in Table 1. As shown in Table 1, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods.

EXAMPLE 2

[0136] A stainless substrate (SUS304) having a size of 5 cm×5 cm and athickness of 0.2 mm was used as a substrate. A first coating solutionand a second coating solution were prepared by mixing the respectivechemical substances having the following components:

[0137] First Coating Solution

[0138] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml

[0139] (2) 1,6-bis(trimethoxysilylethyl)perfluorohexane((CH₃O)₃SiC₂H₄(CF₂)₆C₂H₄Si(OCH₃)₃): 6 ml

[0140] (3) Water: 1 ml

[0141] (4) Hydrochloric acid (36 vol %): 0.1 ml

[0142] Second Coating Solution

[0143] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml 1,6-bis(trimethoxysilyl)hexane((CH₃O)₃Si(CH₂)₆Si(OCH₃)₃): 4 ml

[0144] (2) (2-perfluorooctyl) ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 1 ml

[0145] (3) Water: 1 ml

[0146] (4) Hydrochloric acid (36 vol %): 0.1 ml

[0147] Firstly, the first solution was applied to the substrate underthe condition at 3,000 rpm for 20 seconds, followed by the applicationof the second coating solution at 800 rpm for 20 seconds. Thereafter,the substrate was dried at room temperatures for 1 hour, followed bybaking at 200° C. for 30 minutes. Here, the environment during spincoating was set at a temperature at 24° C. and a relative humidity of34%. A dew point in this environment was 5° C.

[0148] The results of the evaluations of the water-repellent filmprepared in this Example are shown in Table 1. With this example, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods. Here, in this example, the firstlayer functioned so as to improve the adhesion between thewater-repellent film and the substrate, and therefore the wearresistance could be improved compared to Example 1.

EXAMPLE 3

[0149] A water-repellent film was formed in a similar manner to Example2. However, after the second coating solution was applied to thesubstrate, followed by baking at 300° C. for 10 minutes, then the secondcoating solution

[0150] was applied thereto.

[0151] The results of the evaluations of the water-repellent filmprepared in this Example are shown in Table 1. With this example, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods.

EXAMPLE 4

[0152] A stainless substrate (SUS304) having a size of 5 cm×5 cm and athickness of 0.2 mm was used as a substrate.

[0153] A first coating solution, a second coating solution and a thirdcoating solution were prepared by mixing the respective chemicalsubstances having the following components:

[0154] First Coating Solution

[0155] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 50 ml

[0156] (2) Titanium tetra isopropoxide: 10 ml

[0157] (3) Tetraethoxysilane: 2 ml

[0158] (4) Acetylacetone: 3 ml

[0159] (5) Hydrochloric acid (36 vol %): 0.2 ml

[0160] (6) Water: 2 ml

[0161] Second Coating Solution

[0162] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml

[0163] (2) 1,6-bis(trimethoxysilylethyl)perfluorohexane((CH₃O)₃SiC₂H₄(CF₂)₆C₂H₄Si(OCH₃)₃): 6 ml

[0164] (3) Water: 1 ml

[0165] (4) Hydrochloric acid (36 vol %): 0.1 ml

[0166] Third Coating Solution

[0167] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml 1,6-bis(trimethoxysilyl)hexane((CH₃O)₃Si(CH₂)₆Si(OCH₃)₃): 4 ml

[0168] (2) (2-perfluorooctyl) ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 1 ml

[0169] (3) Water: 1 ml

[0170] (4) Hydrochloric acid (36 vol %): 0.1 ml

[0171] Firstly, after the first solution was applied to the substrate byspin coating under the condition at 3,000 rpm for 20 seconds, thesubstrate was dried at room temperatures for 1 hour, followed by bakingat 450° C. for 5 minutes. Next, in the state where the substratereturned to room temperatures, firstly, the second coating solution wasapplied to the substrate under the condition at 3,000 rpm for 20seconds, followed by the application of the third coating solution at800 rpm for 20 seconds. Thereafter, the substrate was dried at roomtemperatures for 1 hour, followed by baking at 200° C. for 30 minutes.Here, the environment during spin coating was set at a temperature of24° C. and a relative humidity of 34%. A dew point in this environmentwas 5° C.

[0172] The results of the evaluations of the water-repellent filmprepared in this Example are shown in Table 1. With this example, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods. Here, in this example, theadherence between the first layer and the substrate or the second layerwas excellent, and therefore the wear resistance could be improvedcompared to Examples 1 and 2.

EXAMPLE 5

[0173] A water-repellent film was formed in a similar manner to Example4. However, after the second coating solution was applied to thesubstrate, followed by baking of the substrate at 300° C. for 10minutes, then the third coating solution was applied thereto.

[0174] The results of the evaluations of the water-repellent filmprepared in this Example are shown in Table 1. With this example, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods.

EXAMPLE 6

[0175] A water-repellent film was formed in a similar manner to Example4. However, instead of 1,6-bis(trimethoxysilyl)hexane,1,2-bis(triethoxysilyl)ethane ((C₂H₅O)₃Si(CH₂)₂Si(OC₂H₅)₃) was used inthe third coating solution.

[0176] The results of the evaluations of the water-repellent filmprepared in this Example are shown in Table 1. With this example, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods.

EXAMPLE 7

[0177] A stainless substrate (SUS304) having a size of 5 cm×5 cm and athickness of 0.2 mm was used as a substrate. The below mentionedsolutions C-1 and C-2 were prepared.

[0178] Solution C-1

[0179] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 30 ml

[0180] (2) 1,4-bis(trimethoxysilylethyl)benzene((CH₃O)₃SiC₂H₄C₆H₄C₂H₄Si(OCH₃)₃): 2 ml

[0181] Hereinafter, this chemical substance will be referred to as asilane coupling agent (A).

[0182] (3) (2-perfluorooctyl)ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 0.2 ml

[0183] Hereinafter, this chemical substance will be referred to as asilane coupling agent (B).

[0184] Solution C-2

[0185] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 19.5 ml

[0186] (2) Pure water: 30 ml

[0187] (3) hydrochloric acid (36 vol %): 0.5 ml

[0188] Small amount of the solution C-2 (5 ml) was dropped into thesolution C-1 while stirring the solution C-1 with a stirrer. Afterdropping, stirring was carried out for about one hour so as to prepare acoating solution. In this coating solution, the mol ratio of purewater/silane coupling agent (A) was about 30 and the mol ratio of thesilane coupling agent (B)/the silane coupling agent (A) was about 0.1.This mixed solution was applied to the substrate by spin coating. Thespin coating was carried out at 3,000 rpm for 20 seconds. Here, theenvironment during spin coating was set at a temperature at 24° C. and arelative humidity of 34%. A dew point in this environment was 5° C.Thereafter, the substrate was dried at room temperature for one hour,followed by baking at 200° C. for 30 minutes.

[0189] The results of the evaluations of the water-repellent filmprepared in this Example are shown in Table 1. With this example, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods.

[0190] Here, since 1,4-bis(trimethoxysilylethyl)benzene used in thisexample includes a benzene ring, this substance is stiffer compared to1,6-bis(trimethoxysilyl)hexane used in Example 1 (the flexibilitypermissible for the molecular structure is reduced), and therefore thismolecule is packed densely and the film density is increased, thusimproving the wear resistance.

[0191] From the results of Table 1, a difference in wear resistancebetween this example and Example 1 cannot be found so much. However,when dry tissue paper (pulp 100%) was used instead of the wetted clothin the wear-resistance test, a difference in their properties becameremarkable. That is to say, when the water-repellent film produced inthis example and the film produced in Example 1 were rubbed with drytissue paper for 500 times and the state of film surface was observed,the film surface of this example had about 10 scratches, whereas, in thecase of Example 1, about 30 scratches were observed. It can be assumedthat, in the state of absence of water, the pulp of the tissue paperfunctioned as an abrasive in the wear-resistance test, by which thedifference in the degree of scratches was generated due to a differencein the density of the film.

EXAMPLE 8

[0192] A water-repellent film was formed in a similar manner to Example2. However, the coating solution of Example 7 was used as the secondcoating solution. The results of the evaluations of the water-repellentfilm prepared in this Example are shown in Table 1. With this example, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods.

[0193] Here, since 1,4-bis(trimethoxysilylethyl)benzene used in thisexample includes a benzene ring, this substance is stiffer compared to1,6-bis(trimethoxysilyl)hexane used in Example 2 (the flexibilitypermissible for the molecular structure is reduced), and therefore thismolecule is packed densely and the film density is increased, thusimproving the wear resistance.

[0194] From the results of Table 1, a difference in wear resistancecannot be found so much. However, when dry tissue paper (pulp 100%) wasused instead of the wetted cloth in the wear-resistance test, adifference in their properties became remarkable. That is to say, whenthe water-repellent film produced in this example and the film producedin Example 2 were rubbed with dry tissue paper for 500 times and thestate of film surface was observed, the film surface of this example hadabout 10 scratches, whereas, in the case of Example 2, about 30scratches were observed. It can be assumed that, in the state of absenceof water, the pulp of the tissue paper functioned as an abrasive in thewear-resistance test, by which the difference in the degree of scratcheswas generated due to a difference in the density of the film.

EXAMPLE 9

[0195] A water-repellent film was formed in a similar manner to Example4. However, the coating solution of Example 7 was used as the thirdcoating solution. The results of the evaluations of the water-repellentfilm prepared in this Example are shown in Table 1. With this example, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods.

[0196] Here, since 1,4-bis(trimethoxysilylethyl)benzene used in thisexample includes a benzene ring, this substance is stiffer compared to1,6-bis(trimethoxysilyl)hexane used in Example 4 (the flexibilitypermissible for the molecular structure is reduced), and therefore thismolecule is packed densely and the film density is increased, thusimproving the wear resistance.

[0197] From the results of Table 1, a difference in wear resistancecannot be found so much. However, when dry tissue paper (pulp 100%) wasused instead of the wetted cloth in the wear-resistance test, adifference in their properties became remarkable. That is to say, whenthe water-repellent film produced in this example and the film producedin Example 4 were rubbed with dry tissue paper for 500 times and thestate of film surface was observed, the film surface of this example hadabout 10 scratches, whereas, in the case of Example 4, about 30scratches were observed. It can be assumed that, in the state of absenceof water, the pulp of the tissue paper functioned as an abrasive in thewear-resistance test, by which the difference in the degree of scratcheswas generated due to a difference in the density of the film.

EXAMPLE 10

[0198] A water-repellent film was formed in a similar manner to Example4. However, the coating solution of Example 7 was used as the thirdcoating solution. In addition, the baking temperature after theapplication of the third coating solution was set at 300° C. for 15minutes.

[0199] The results of the evaluations of the water-repellent filmprepared in this Example are shown in Table 1. With this example, awater-repellent film with high alkali resistance and excellent wearresistance could be realized as compared to the water-repellent filmsproduced by the conventional methods.

[0200] Here, since the third-layer water-repellent film used in thisexample had high heat resistance because it included a benzene ring,this film could be baked at a higher temperature compared to the filmproduced in Example 4, for example, that included a hydrocarbon chainonly. Generally, as the baking temperature increases, the dehydrationpolymerization reaction of the silane coupling agent increasinglyproceeds and a polymer film with a higher density can be formed, so thatthe hardness of the film and the adhesion thereof to the substrateincreases. Therefore, as shown in Table 1 as well, the water-repellentfilm produced in this example has higher wear resistance compared withthe other water-repellent films that were baked at 200° C.

[0201] Furthermore, similarly, a difference in wear-resistance from thefilm produced in Example 9 was examined. When dry tissue paper (pulp100%) was used instead of the wetted cloth in the wear-resistance test,a difference in their properties became remarkable. That is to say, whenthe water-repellent film produced in this example and the film producedin Example 9 were rubbed with dry tissue paper for 500 times and thestate of film surface was observed, the film produced in this examplehad no scratches on the surface thereof, whereas, in the case of Example9, about 10 scratches were generated. This indicates that, even when thesame coating solution is applied, the wear resistance can be improved inthe film of this example that was baked at a high temperature than inthe film of Example 9 baked at a lower temperature. TABLE 1 EvaluationResults of Water-repellent Films Produced in Examples and ComparativeExamples Static contact angle to water (deg) Value after soaked in Valueafter Types of water Initial solution of pH = 8 at wear-resistance testrepellent films value 70° C. for 100 hours with wetted cloth Example 1101 100 92 Example 2 101 100 95 Example 3 101 100 98 Example 4 101 101100 Example 5 101 101 100 Example 6 101 100 100 Example 7 101 100 100Example 8 101 100 100 Example 9 101 100 100 Example 10 101 100 101 Comp.Example 1 110 15 109 Comp. Example 2 104 5 (film was dissolved) 103

EXAMPLE 11

[0202] A stainless substrate (SUS304) having a size of 3 cm×3 cm and athickness of 100 μm was used as a substrate. A coating solution wasprepared by mixing chemical substances having the following components:

[0203] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml

[0204] (2) 1,6-bis(trimethoxysilyl)hexane ((CH₃O)₃Si(CH₂)₆Si(OCH₃)₃): 4ml

[0205] (3) (2-perfluorooctyl)ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 1 ml

[0206] (4) Water: 1 ml

[0207] (5) Hydrochloric acid (36 vol %): 0.1 ml

[0208] The mixed solution of these was applied to the substrate by spincoating. The spin coating was carried out at 800 rpm for 20 seconds.

[0209] Thereafter, the substrate was dried at room temperatures for 1hour, followed by baking at 200° C. for 30 minutes. Here, theenvironment during spin coating was set at a temperature at 24° C. and arelative humidity of 34%. A dew point in this environment was 5° C.Thereafter, 400 through holes for nozzles having a diameter of 30 μmwere bored in the substrate to form an ink jet nozzle (hereinafterdescribed as a nozzle plate), and this was assembled as a print head,which was incorporated into an ink jet printer.

[0210] Evaluations of the nozzle plate were conducted in terms of thefollowing four items: here, the ink used in the evaluations was blackink with pH=9.0 and a surface tension of 35 dyn/cm. The ink was preparedby mixing black dye, glycerin, a penetrant, a pH adjustor and water at apredetermined ratio. The evaluations (A) to (C) were conducted using asubstrate without nozzle holes.

[0211] A. Evaluation of Water Repellency

[0212] A static contact angle and a receding contact angle of awater-repellent film to the ink were measured. Furthermore, about 30 μlof ink was dropped onto the nozzle plate, and was wiped with a rubberblade made of polybutadiene, having a size of 5 mm×30 mm and a thicknessof 1 mm so as to examine whether the ink remained or not. Morespecifically, the rubber blade was arranged perpendicular to the nozzleplate face so that a side with a length of 5 mm contacted with thenozzle plate, and was moved in one direction to remove the ink. Visualinspection was made as to whether the ink was removed or not.

[0213] B. Ink Resistance Property

[0214] After the nozzle plate was soaked in the ink, the plate wasallowed to stand at 70° C. for 500 hours. Then, after the plate wastaken out and was washed with pure water, a static contact angle and areceding contact angle to the ink were measured. In addition, theink-removable property also was evaluated in the same manner as in (A).

[0215] C. Wear-Resistance Property

[0216] A rubber blade made of polybutadiene, having a size of 5 mm×30 mmand a thickness of 1 mm, was arranged perpendicular to the nozzle plateface so that a side with a length of 5 mm contacted with the nozzleplate, and the rubber blade was pressed by about 2 mm toward the nozzleplate. Then, in this state, the plate was rubbed with the side with alength of 5 mm for 50,000 times. After that, a static contact angle anda receding contact angle of the nozzle plate to the ink were measured.

[0217] D. Evaluation of Print Property

[0218] After the nozzle plate was soaked in the ink and was allowed tostand at 70° C. for 500 hours, this nozzle plate was assembled as aprint head, which was incorporated into a printer. Then, printing wasconducted with this printer. A print quality was compared with thatprinted with a nozzle plate that was not thus treated. The results ofthe evaluations of the water-repellent film produced in this example areshown in Table 2.

[0219] (1) Evaluation of the result (A): A static contact angle and areceding contact angle of the ink to a fluororesin that was polished tobe the closest possible to a mirror surface were both 70 deg. Therefore,it can be considered that the water-repellent film having a value closerto this value has an ink-repellent property equivalent to thefluororesin. Furthermore, as a value of the static contact angle becomescloser to a value of the receding contact angle, the remaining ink ismore easily removed when the nozzle surface is wiped with a rubberblade. From these results, the ink-repellent property equivalent to thefluororesin could not be obtained, but the ink could be repelledsufficiently and the remaining ink could be removed completely by wipingit with the rubber blade. Therefore, these results indicate that awater-repellent film with a good ink-repellency could be realized.

[0220] (2) Evaluation of the result (B): Although the contact angle tothe ink was decreased after the test, it was confirmed that, even in thecase of this value of static contact angle, the ink could be repelledsufficiently and the remaining ink could be removed completely by wipingit with the rubber blade. Therefore, the results indicate that awater-repellent film having durability against ink could be realized.

[0221] (3) Evaluation of the result (C): The value of the contact anglehardly changed. Therefore, this result indicates that a water-repellentfilm having wear-resistance could be realized.

[0222] (4) Evaluation of the result (D): The discharge property wasfavorable like the nozzle plate before the test. From this result, it isindicated that a nozzle plate having durability against ink could berealized.

[0223] From these results, a nozzle plate that was applicable to an inkjet printer could be realized. Here, in this example, the mixed solutionof ethanol and 2,2,2-trifluoroethanol was used as a solvent of thecoating solution. This solution has good wettability with the substrate,so that this solution allows easy formation of a uniform water-repellentfilm. Furthermore, in the silane coupling agent having a hydrocarbonchain, the number of carbons that constitute the carbon chain was set at6. This value is sufficient for preventing an alkaline component fromintruding into the film and is capable of forming a high-density filmwith excellent wear resistance.

EXAMPLE 12

[0224] A stainless substrate (SUS304) having a size of 3 cm×3 cm and athickness of 100 μm was used as a substrate. A first coating solutionand a second coating solution were prepared by mixing the respectivechemical substances having the following components:

[0225] 1. First Coating Solution

[0226] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml

[0227] (2) 1,6-bis(trimethoxysilylethyl)perfluorohexane((CH₃O)₃SiC₂H₄(CF₂)₆C₂H₄Si(OCH₃)₃): 6 ml

[0228] (3) Water: 1 ml

[0229] (4) Hydrochloric acid (36 vol %): 0.1 ml

[0230] 2. Second Coating Solution

[0231] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml

[0232] (2) 1,6-bis(trimethoxysilyl)hexane ((CH₃O)₃Si(CH₂)₆Si(OCH₃)₃): 4ml

[0233] (3) (2-perfluorooctyl) ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 1 ml

[0234] (4) Water: 1 ml

[0235] (5) Hydrochloric acid (36 vol %): 0.1 ml

[0236] The mixed solution of these was applied to the substrate by spincoating. Firstly, the first coating solution was applied to thesubstrate under the condition at 3,000 rpm for 20 seconds, followed bythe application of the second coating solution at 800 rpm for 20seconds. Thereafter, the substrate was dried at room temperatures for 1hour, followed by baking at 200° C. for 30 minutes. Here, theenvironment during spin coating was set at a temperature at 24° C. and arelative humidity of 34%. A dew point in this environment was 5° C. Theresults of evaluations of the water-repellent film produced in thisexample are shown in Table 2.

[0237] 1. Evaluation of the result (A): It is indicated that awater-repellent film with a good ink-repellency could be realized.

[0238] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0239] 3. Evaluation of the result (C): It is indicated that awater-repellent film with wear resistance could be realized.

[0240] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized.

[0241] From these results, a nozzle plate that was applicable to an inkjet printer could be realized.

[0242] Here, in this example,1,8-bis(trimethoxysilylethyl)perfluorohexane was used as the silanecoupling agent that constitutes the first-layer film. The length of afluorocarbon chain in this coupling agent is sufficient for preventingan alkaline component from intruding into the film and is capable offorming a high-density film with excellent wear resistance.

EXAMPLE 13

[0243] A water-repellent film was formed in a similar manner to Example12. However, after the second coating solution was applied to thesubstrate, followed by baking of the substrate at 300° C. for 10minutes, then the second coating solution was applied thereto. Theresults of evaluations of the water-repellent film produced in thisexample are shown in Table 2.

[0244] 1. Evaluation of the result (A): It is indicated that awater-repellent film with a good ink-repellency could be realized.

[0245] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0246] 3. Evaluation of the result (C): It is indicated that awater-repellent film with wear resistance could be realized.

[0247] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized.

[0248] From these results, a nozzle plate that was applicable to an inkjet printer could be realized. Example 14

[0249] A stainless substrate (SUS304) having a size of 3 cm×3 cm and athickness of 100 μm was used as a substrate. A first coating solution, asecond coating solution and a third coating solution were prepared bymixing the respective chemical substances having the followingcomponents:

[0250] 1. First Coating Solution

[0251] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 50 ml

[0252] (2) Titanium tetra isopropoxide: 10 ml

[0253] (3) Tetraethoxysilane: 2 ml

[0254] (4) Acetylacetone: 3 ml

[0255] (5) Hydrochloric acid (36 vol %): 0.2 ml

[0256] (6) Water: 2 ml

[0257] 2. Second Coating Solution

[0258] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml

[0259] (2) 1,8-bis(trimethoxysilylethyl)perfluorohexane((CH₃O)₃SiC₂H₄(CF₂)₆C₂H₄Si(OCH₃)₃): 6 ml

[0260] (3) Water: 1 ml

[0261] (4) Hydrochloric acid (36 vol %): 0.1 ml

[0262] 3. Third Coating Solution

[0263] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml

[0264] (2) 1,6-bis(trimethoxysilyl)hexane ((CH₃O)₃Si(CH₂)₆Si(OCH₃)₃): 4ml

[0265] (3) (2-perfluorooctyl) ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 1 ml

[0266] (4) Water: 1 ml

[0267] (5) Hydrochloric acid (36 vol %): 0.1 ml

[0268] Firstly, after the first solution was applied to the substrate byspin coating at 3,000 rpm for 20 seconds, the substrate was dried atroom temperatures for 1 hour, followed by baking at 450° C. for 5minutes. Next, in the state where the substrate returned to roomtemperatures, the second coating solution was applied to the substrateunder the condition at 3,000 rpm for 20 seconds, followed by theapplication of the third coating solution at 800 rpm for 20 seconds.Thereafter, the substrate was dried at room temperatures for 1 hour,followed by baking at 200° C. for 30 minutes. Here, the environmentduring spin coating was set at a temperature of 24° C. and a relativehumidity of 34%. A dew point in this environment was 5° C.

[0269] The results of evaluations of the water-repellent film producedin this example are shown in Table 2.

[0270] 1. Evaluation of the result (A): It is indicated that awater-repellent film with a good ink-repellency could be realized.

[0271] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0272] 3. Evaluation of the result (C): It is indicated that awater-repellent film with wear resistance could be realized.

[0273] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized.

[0274] From these results, a nozzle plate that was applicable to an inkjet printer could be realized.

[0275] Here, in this example, the volume ratio of the siliconalkoxideand the titanalkoxide as components of the first-layer film was set at2:10. This value is set so as to prevent the film from being destroyedby the alkaline component and so as to realize a sufficient density ofhydroxyl groups on the surface thereof that brings the second-layer filminto intimate contact thereto.

EXAMPLE 15

[0276] A water-repellent film was formed in a similar manner to Example14. However, after the second coating solution was applied to thesubstrate, followed by baking of the substrate at 300° C. for 10minutes, then the third coating solution was applied thereto. Theresults of evaluations of the water-repellent film produced in thisexample are shown in Table 2.

[0277] 1. Evaluation of the result (A): It is indicated that awater-repellent film with a good ink-repellency could be realized.

[0278] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0279] 3. Evaluation of the result (C): It is indicated that awater-repellent film with wear resistance could be realized.

[0280] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized.

[0281] From these results, a nozzle plate that was applicable to an inkjet printer could be realized.

EXAMPLE 16

[0282] A water-repellent film was formed in the similar manner as inExample 14. However, instead of 1,6-bis(trimethoxysilyl)hexane as in thethird coating solution, 1,2-bis(triethoxysilyl)ethane((C₂H₅O)₃Si(CH₂)₂Si(OC₂H₅)₃) was used. The results of evaluations of thewater-repellent film produced in this example are shown in Table 2.

[0283] 1. Evaluation of the result (A): It is indicated that awater-repellent film with a good ink-repellency could be realized.

[0284] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0285] 3. Evaluation of the result (C): It is indicated that awater-repellent film with wear resistance could be realized.

[0286] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized.

[0287] From these results, a nozzle plate that was applicable to an inkjet printer could be realized.

EXAMPLE 17

[0288] A stainless substrate (SUS304) having a size of 3 cm×3 cm and athickness of 1001 m was used as a substrate. The below mentionedsolutions C-1 and C-2 were prepared.

[0289] Solution C-1

[0290] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 30 ml

[0291] (2) 1,4-bis(trimethoxysilylethyl)benzene((CH₃O)₃SiC₂H₄C₆H₄C₂H₄Si(OCH₃)₃): 2 ml

[0292] Hereinafter, this chemical substance will be referred to as asilane coupling agent (A).

[0293] (3) (2-perfluorooctyl)ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 0.2 ml

[0294] Hereinafter, this chemical substance will be referred to as asilane coupling agent (B).

[0295] Solution C-2

[0296] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 19.5 ml

[0297] (2) Pure water: 30 ml

[0298] (3) Hydrochloric acid (36 vol %): 0.5 ml

[0299] A small amount of the solution C-2 (5 ml) was dropped into thesolution C-1 while stirring the solution C-1 with a stirrer. Afterdropping, stirring was carried out for about one hour so as to prepare acoating solution. In this coating solution, the mol ratio of purewater/the silane coupling agent (A) was about 30 and the mol ratio ofthe silane coupling agent (B)/the silane coupling agent (A) was about0.1. Similarly to Example 11, this mixed solution was applied to thesubstrate by spin coating. The spin coating was carried out at 3,000 rpmfor 20 seconds. Here, the environment during spin coating was set at atemperature of 24° C. and a relative humidity of 34%. A dew point inthis environment was 5° C. Thereafter, the substrate was dried at roomtemperature for one hour, followed by baking at 200° C. for 30 minutes.

[0300] The results of evaluations of the water-repellent film producedin this example are shown in Table 2.

[0301] Evaluation of the result (A): It is indicated that awater-repellent film with a good ink-repellency could be realized.

[0302] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0303] 3. Evaluation of the result (C): It is indicated that awater-repellent film with wear resistance could be realized.

[0304] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized.

[0305] From these results, a nozzle plate that was applicable to an inkjet printer could be realized.

[0306] Here, since 1,4-bis(trimethoxysilylethyl)benzene used in thisexample includes a benzene ring, this substance is stiffer compared to1,6-bis(trimethoxysilyl)hexane used in Example 11 (the flexibilitypermissible for the molecular structure is reduced), and therefore thismolecule is packed densely and the film density is increased, thusimproving the wear resistance.

[0307] From the results of Table 2, a difference in wear resistance isnot so great. However, when the wear resistance test was performed inthe presence of pigment ink, a difference in their properties becameremarkable. That is to say, when the water-repellent film produced inthis example and the film produced in Example 11 were rubbed with acotton swab impregnated with the pigment ink for 100 times and the stateof film surface was observed, the film surface of this example had about10 scratches, whereas, in the case of Example 11, about 30 scratcheswere observed. It can be assumed that, since the pigment ink contained ahard inorganic substance, this substance functioned as an abrasive inthe wear-resistance test, by which the difference in the degree ofscratches was generated due to a difference in the density of the film.

EXAMPLE 18

[0308] A water-repellent film was formed in a similar manner to Example12. However, the coating solution of Example 17 was used as the secondcoating solution. The results of evaluations of the water-repellent filmproduced in this example are shown in Table 2.

[0309] 1. Evaluation of the result (A): It is indicated that awater-repellent film with a good ink-repellency could be realized.

[0310] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0311] 3. Evaluation of the result (C): It is indicated that awater-repellent film with wear resistance could be realized.

[0312] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized.

[0313] From these results, a nozzle plate that was applicable to an inkjet printer could be realized.

[0314] Here, since 1,4-bis(trimethoxysilylethyl)benzene used in thisexample includes a benzene ring, this substance is stiffer compared to1,6-bis(trimethoxysilyl)hexane used in Example 12 (the flexibilitypermissible for the molecular structure is reduced), and therefore thismolecule is packed densely and the film density is increased, thusimproving the wear resistance.

[0315] From the results of Table 2, a difference in wear resistancecannot be found so much. However, when the wear resistance test wasperformed in the presence of pigment ink, a difference in theirproperties became remarkable. That is to say, when the water-repellentfilm produced in this example and the film produced in Example 12 wererubbed with a cotton swab impregnated with the pigment ink for 100 timesand the state of film surface was observed, the film surface of thisexample had about 10 scratches, whereas, in the case of Example 11,about 30 scratches were observed. It can be assumed that, since thepigment ink contained a hard inorganic substance, this substancefunctioned as an abrasive in the wear-resistance test, by which thedifference in the degree of scratches was generated due to a differencein the density of the film.

EXAMPLE 19

[0316] A water-repellent film was formed in the same manner as inExample 14. However, the coating solution of Example 17 was used as thethird coating solution. The results of evaluations of thewater-repellent film produced in this example are shown in Table 2.

[0317] 1. Evaluation of the result (A): It is indicated that awater-repellent film with a good ink-repellency could be realized.

[0318] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0319] 3. Evaluation of the result (C): It is indicated that awater-repellent film with wear resistance could be realized.

[0320] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized.

[0321] From these results, a nozzle plate that was applicable to an inkjet printer could be realized.

[0322] Here, since 1,4-bis(trimethoxysilylethyl)benzene used in thisexample includes a benzene ring, this substance is stiffer compared to1,6-bis(trimethoxysilyl)hexane used in Example 14 (the flexibilitypermissible for the molecular structure is reduced), and therefore thismolecule is packed densely and the film density is increased, thusimproving the wear resistance.

[0323] From the results of Table 2, a difference in wear resistance isnot so great. However, when the wear resistance test was performed inthe presence of pigment ink, a difference in their properties becameremarkable. That is to say, when the water-repellent film produced inthis example and the film produced in Example 14 were rubbed with acotton swab impregnated with ink for 100 times and the state of filmsurface was observed, the film surface of this example had about 10scratches, whereas, in the case of Example 11, about 30 scratches wereobserved. It can be assumed that, since the pigment ink contained a hardinorganic substance, this substance functioned as an abrasive in thewear-resistance test, by which the difference in the degree of scratcheswas generated due to a difference in the density of the film.

EXAMPLE 20

[0324] A water-repellent film was formed in the similar manner as inExample 14. However, the coating solution of Example 17 was used as thethird coating solution. In addition, the baking temperature after theapplication of the third coating solution was set at 300° C. for 15minutes. The results of evaluations of the water-repellent film producedin this example are shown in Table 2.

[0325] 1. Evaluation of the result (A): It is indicated that awater-repellent film with a good ink-repellency could be realized.

[0326] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0327] 3. Evaluation of the result (C): It is indicated that awater-repellent film with wear resistance could be realized.

[0328] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized.

[0329] From these results, a nozzle plate that was applicable to an inkjet printer could be realized.

[0330] Here, since the third-layer water-repellent film used in thisexample had a high heat resistance because it included a benzene ring,this film could be baked at a higher temperature compared to the filmproduced in Example 14, for example, that included a hydrocarbon chainonly. Generally, as the baking temperature increases, the dehydrationpolymerization reaction of the silane coupling agent increasinglyproceeds and a polymer film with a higher density can be formed, so thatthe hardness of the film and the adhesion thereof to the substrateincreases. Therefore, the water-repellent film produced in this examplehas higher wear resistance compared with the other water-repellent filmsthat were baked at 200° C.

[0331] From the results of Table 2, a difference in wear resistance isnot so great. However, when the wear resistance test was performed inthe presence of pigment ink, a difference in their properties becameremarkable. That is to say, when the water-repellent film produced inthis example and the film produced in Example 14 were rubbed with acotton swab impregnated with the pigment ink for 100 times and the stateof film surface was observed, the film surface of this example had about10 scratches, whereas, in the case of Example 14, about 30 scratcheswere observed. It can be assumed that, since the pigment ink contained ahard inorganic substance, this substance functioned as an abrasive inthe wear-resistance test, by which the difference in the degree ofscratches was generated due to a difference in the density of the film.

[0332] Furthermore, similarly, a difference in wear-resistance from thefilm produced in Example 19 was examined. To this end, the film surfacewas rubbed with a cotton swab wetted with pigment ink for 1,000 times toexamine the difference for both films. As a result, the film produced inthis example had about 20 scratches on the surface thereof, whereas thefilm produced in Example 19 had about 50 scratches on the surfacethereof. This indicates that, even when the same coating solution isapplied, the wear resistance can be improved in the film of this examplethat was baked at a high temperature versus the film of Example 19 bakedat a lower temperature.

EXAMPLE 21

[0333] A stainless substrate (SUS304) having a size of 3 cm×3 cm and athickness of 100 μm was used as a substrate. A first coating solutionand a second coating solution were prepared by mixing the respectivechemical substances having the following components:

[0334] 1. First Coating Solution

[0335] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 50 ml

[0336] Titanium tetra isopropoxide: 10 ml

[0337] (2) Tetraethoxysilane: 2 ml

[0338] (3) Acetylacetone: 3 ml

[0339] (4) Hydrochloric acid (36 vol %): 0.2 ml

[0340] (5) Water: 2 ml

[0341] 2. Second Coating Solution

[0342] (1) Mixed solution of ethanol and 2,2,2-trifluoroethanol (mixingat the volume ratio of 8:2): 60 ml

[0343] (2) (2-perfluorooctyl) ethyltrimethoxysilane(CF₃(CF₂)₇C₂H₄Si(OCH₃)₃): 6 ml

[0344] (3) Water: 1 ml

[0345] (4) Hydrochloric acid (36 vol %): 0.1 ml

[0346] Firstly, after the first solution was applied to the substrate byspin coating under the condition at 3,000 rpm for 20 seconds, thesubstrate was dried at room temperatures for 1 hour, followed by bakingat 450° C. for 5 minutes. Next, in the state where the substratereturned to room temperatures, the second coating solution was appliedto the substrate under the condition at 800 rpm for 20 seconds, and thenthe substrate was dried at room temperatures for 1 hour, followed bybaking at 300° C. for 30 minutes. The results of evaluations of thewater-repellent film produced in this example are shown in Table 2.

[0347] 1. Evaluation of the result (A): It can be estimated that thereason for the static contact angle being larger than the value withrespect to a fluororesin is that the unevenness of the surface of thesecond-layer film is large. Generally, as the unevenness of the surfaceincreases, there is a tendency that a receding contact angle is reduced.This result also can be affected by the tendency. However, in spite ofthe presence of such unevenness, ink could be wiped away sufficiently.Therefore, the result indicates that a water-repellent film with a goodink-repellency could be realized.

[0348] 2. Evaluation of the result (B): It is indicated that awater-repellent film with durability against ink could be realized.

[0349] 3. Evaluation of the result (C): After the test, the staticcontact angle and the receding contact angle were reduced. In addition,the values of the static contact angle and the receding contact anglebecame smaller. This indicates that a part of the surface of thesecond-layer water-repellent film was ground by the wear-resistance testso as to make the unevenness of the surface flat. When an evaluation wasconducted in this state as to whether the ink can be wiped away or not,the ink could be removed completely. Therefore, it is indicated that awater-repellent film with wear resistance could be realized.

[0350] 4. Evaluation of the result (D): It is indicated that a nozzleplate with durability against ink could be realized. TABLE 2 EvaluationResults of Water-repellent Films Produced in Examples Contact angle toink (static contact angle-receding contact angle: unit deg) Types ofValue after Print property water soaked in After rub- after soaked inrepellent Initial ink at 70° C. bing for ink at 70° C. films value for500 hrs 100,000 times for 500 hrs Example 11 61-59 50-48 61-59 goodExample 12 62-60 50-48 62-60 good Example 13 62-61 50-48 62-61 goodExample 14 62-61 50-48 62-61 good Example 15 62-61 50-48 62-61 goodExample 16 62-61 45-40 62-61 good Example 17 65-62 55-52 65-62 goodExample 18 66-62 55-52 66-62 good Example 19 66-62 55-52 66-62 goodExample 20 66-62 55-52 66-62 good Example 21 90-70 70-40 70-60 good

[0351] From these results, water-repellent films having alkaliresistance could be realized. In addition, using these films, nozzleplates that were applicable to an ink jet printer could be realized.Here, in the embodiments and the examples of the present invention, analkoxysilane compound only is described as the silane coupling agent.However, the silane coupling agent is not limited to this, and if thewater content is controlled strictly, similar water-repellent films canbe formed using a chlorosilane compound, a silazane compound and thelike that have high reactivity. Furthermore, although spin coating isused for the application method in all of the examples, the applicationmethod is not limited to this, and needless to say, a dip method, aspray method and the like can be used. Furthermore, in the examples ofthe present invention, the water-repellent films utilize some sorts ofsilane coupling agents, ethanol and 2,2,2-trifluoroethanol as thesolvents, and hydrochloric acid as the acidic catalyst, which are notlimiting ones. For example, as the solvent, propanol, butanol and amixture thereof are available, and as the acidic catalyst, nitric acid,acetic acid, formic acid, etc. are available. Furthermore, thecompositions of the coating solution are not limited to those describedin the embodiments, and two or more types of silane coupling agents canbe combined. In addition, for example, an inhibitor, a thickener such aspolyethylene glycol and a surface-active agent for controlling thesurface tension can be used. Furthermore, the amount of the silanecoupling agent can be varied depending on an intended use, for example,in order to improve the water repellency, the amount of silane couplingagent having a fluoroalkyl chain may be increased. In addition, in theexamples, the nozzle holes are all bored by electrical dischargemachining. However, the method is not limited to this, and lasermachining, punching machining, etching machining and the like can beused.

INDUSTRIAL APPLICABILITY

[0352] As stated above, according to the present invention, awater-repellent film having high alkali resistance can be realized usinga silane coupling agent.

[0353] The water-repellent film of the present invention includes afluoroalkyl chain, so as to have a low surface energy. Therefore, thefilm can repel various kinds of liquid such as oil, in addition towater, and a solid substance that adheres to this film can be removedeasily. Therefore, the water-repellent film is useful as an antifoulingfilm applicable to household equipment, for example, cooking equipmentor a bedpan, to which dirt tends to attach. In particular, thewater-repellent film of the present invention is useful as anantifouling film of a part exposed to a high alkali detergent.Furthermore, the water-repellent film of the present invention isapplicable to various fields, for example, application to a part that isalways exposed to an alkaline solution.

1. A water-repellent film that is formed on a solid substrate,comprising: a molecule (A) comprising at least one or more of siloxanebonding (—Si—O—) at both ends and a hydrocarbon chain in a middle part;and a molecule (B) comprising a fluorocarbon chain at one end and atleast one or more of siloxane bonding (—Si—O—) at another end, wherein apolymer film is formed at least with the molecule (A) and the molecule(B).
 2. The water-repellent film according to claim 1, wherein, betweenthe solid substrate and the water-repellent film, a first lower polymerfilm further is formed, the first lower polymer film being configuredwith a molecule comprising at least one or more of siloxane bonding(—Si—O—) at both ends and a fluorocarbon chain in a middle part.
 3. Thewater-repellent film according to claim 2, wherein, between the solidsubstrate and the first lower polymer film, a second lower oxide film isformed, the second lower oxide film being made of a mixture of a siliconoxide and a titanium oxide.
 4. The water-repellent film according toclaim 1, wherein a density of the molecule (B) in the vicinity of theoutermost surface of the water-repellent film is higher than a densityof the molecule (B) inside the water-repellent film.
 5. Thewater-repellent film according to claim 1, wherein a ratio of themolecule (A) and the molecule (B) is in the range from 0.001 to 0.2(=the molecule (B)/the molecule (A)) that is represented by a mol ratio.6. The water-repellent film according to claim 1, wherein the molecule(A) comprises a straight-chain hydrocarbon chain.
 7. The water-repellentfilm according to claim 1, wherein the molecule (A) comprises a benzenering.
 8. The water-repellent film according to claim 6, wherein thenumber of carbons that constitute the straight-chain hydrocarbon chainranges from 1 to 10, inclusive.
 9. A water-repellent film that is formedon a solid substrate and is made up of a two-layered thin film, whereina first-layer film contacting with the substrate is made of a mixture ofa silicon oxide and a titanium oxide, a ratio of the silicon to thetitanium being in the range from 10% to 30%, inclusive, in terms ofmols, and a second-layer film formed on the first-layer film is apolymer film that is at least one selected from a hydrolyzate and adehydrated polymer of a silane coupling agent comprising a fluorocarbonchain.
 10. A method for producing a water-repellent film on a solidsubstrate, comprising the steps of: applying a coating solution to thesubstrate, wherein the coating solution is prepared by mixing a silanecoupling agent (A) comprising reactive functional groups at both endsand comprising a hydrocarbon chain in a middle part, a silane couplingagent (B) comprising a fluorocarbon chain at one end and a reactivefunctional group at another end, an organic solvent, water and an acidiccatalyst, and heating the substrate so as to form a polymer film withthe silane coupling agent (A) and the silane coupling agent (B).
 11. Themethod for producing a water-repellent film according to claim 10,wherein between the solid substrate and the water-repellent film, apolymer film further is formed by applying a first underlayer coatingsolution to the substrate, wherein the first underlayer coating solutionis prepared by mixing a silane coupling agent comprising reactivefunctional groups at both ends and comprising a fluorocarbon chain in amiddle part, an organic solvent, water and an acidic catalyst.
 12. Themethod for producing a water-repellent film according to claim 11,wherein after the first underlayer coating solution is applied to thesolid substrate, followed by heating at 100° C. to 300° C., inclusive,then a coating solution comprising the silane coupling agent (A) and thesilane coupling agent (B) is applied thereto.
 13. The method forproducing a water-repellent film according to claim 11, wherein, betweenthe solid substrate and the first underlayer polymer film, an oxide filmthat is made of a silicon oxide and a titanium oxide further is formedby applying a second underlayer coating solution to the substrate,followed by baking, wherein the second underlayer coating is prepared bymixing titanalkoxide, siliconalkoxide, an organic solvent, water and anacidic catalyst.
 14. The method for producing a water-repellent filmaccording to claim 10, wherein the molecule (A) comprises astraight-chain hydrocarbon chain.
 15. The method for producing awater-repellent film according to claim 10, wherein the molecule (A)comprises a benzene ring.
 16. The method for producing a water-repellentfilm according to claim 10, wherein the reactive functional groups ofthe silane coupling agents are alkoxysilyl groups.
 17. The method forproducing a water-repellent film according to claim 10, wherein thenumber of carbons that constitute the straight-chain hydrocarbon chainranges from 1 to 10, inclusive.
 18. The method for producing awater-repellent film according to claim 10, wherein the molecule (A)comprises a benzene ring, and a mol ratio of water and the molecule (A)is in the range from 20 to 150 (=water/the molecule (A)).
 19. The methodfor producing a water-repellent film according to claim 10, wherein amol ratio of the molecule (A) and the molecule (B) is in the range from0.001 to 0.2 (=the molecule (B)/the molecule (A)).
 20. The method forproducing a water-repellent film according to claim 10, wherein theorganic solvent of the coating solution comprising the silane couplingagent (B) comprises alcohol having fluorocarbon.
 21. The method forproducing a water-repellent film according to claim 10, wherein a dewpoint of atmosphere for applying the coating solution to the substrateis lower than a temperature of the atmosphere by 5° C. or more.
 22. Themethod for producing a water-repellent film according to claim 10,wherein a method for applying the coating solution to a surface of thesubstrate is at least one selected from a dipping method, a sprayingmethod, a brushing method, a method using a cloth, a spin coatingmethod, a method using a roller, a knife coating method and a filmcoating method.
 23. A method for producing a water-repellent film on asolid substrate, comprising the steps of: applying a first coatingsolution to the substrate, followed by baking at 300° C. or higher,where the first coating solution is prepared by mixing titanalkoxide,siliconalkoxide, an organic solvent, water and an acidic catalyst, andapplying a second coating solution to the substrate, followed by baking,where the second coating solution is prepared by mixing a silanecoupling agent having a fluorocarbon chain, an organic solvent, waterand an acidic catalyst, wherein in the first coating solution, a ratioof the siliconalkoxide to the titanalkoxide is in the range from 10% to30%, inclusive, in terms of mols.
 24. The method for producing awater-repellent film according to claim 23, wherein a method forapplying the coating solution to a surface of the substrate is at leastone selected from a dipping method, a spraying method, a brushingmethod, a method using a cloth, a spin coating method, a method using aroller, a knife coating method and a film coating method.
 25. An ink jethead comprising an ink jet nozzle, wherein a water-repellent film isformed on an ink-discharging side of a substrate of the ink jet nozzlehaving a nozzle hole from which ink is discharged, wherein thewater-repellent film comprises a molecule (A) comprising at least one ormore of siloxane bonding (—Si—O—) at both ends and a hydrocarbon chainin a middle part; and a molecule (B) comprising a fluorocarbon chain atone end and at least one or more of siloxane bonding (—Si—O—) at anotherend, and wherein a polymer film is formed at least with the molecule (A)and the molecule (B).
 26. An ink jet type recording apparatus,comprising: an ink jet head in which a water-repellent film is formed onan ink-discharging side of a substrate having a nozzle hole from whichink is discharged, wherein the water-repellent film comprises a molecule(A) comprising at least one or more of siloxane bonding (—Si—O—) at bothends and a hydrocarbon chain in a middle part; and a molecule (B)comprising a fluorocarbon chain at one end and at least one or more ofsiloxane bonding (—Si—O—) at another end, and wherein a polymer film isformed at least with the molecule (A) and the molecule (B); and a movingunit for relative movement of a recording medium.